Fix gcc-12 compiler warnings on lkcd_*.c

Without the patch, the following gcc-12 compiler warnings are emitted
for lkcd_*.c:

lkcd_v1.c: In function 'dump_lkcd_environment_v1':
lkcd_v1.c:252:20: warning: the comparison will always evaluate as 'true' for the address of 'dh_panic_string' will never be NULL [-Waddress]
  252 |                 dh && dh->dh_panic_string &&
      |                    ^~
In file included from lkcd_v1.c:21:
lkcd_vmdump_v1.h:108:30: note: 'dh_panic_string' declared here
  108 |         char                 dh_panic_string[DUMP_PANIC_LEN];
      |                              ^~~~~~~~~~~~~~~
...

Reported-by: Lianbo Jiang <[email protected]>
Signed-off-by: Kazuhito Hagio <[email protected]>

Author: k-hagio

lkcd_v1.c

@@ -249,8 +249,7 @@ dump_lkcd_environment_v1(ulong arg)
         lkcd_print("          dh_eip: %lx\n", dh->dh_eip);
 	lkcd_print("    dh_num_pages: %d\n", dh->dh_num_pages);
         lkcd_print(" dh_panic_string: %s%s", dh->dh_panic_string,
-		dh && dh->dh_panic_string &&
-		strstr(dh->dh_panic_string, "\n") ? "" : "\n");
+		dh && strstr(dh->dh_panic_string, "\n") ? "" : "\n");
         lkcd_print("         dh_time: %s\n",
                         strip_linefeeds(ctime(&(dh->dh_time.tv_sec))));
 

lkcd_v2_v3.c

@@ -307,8 +307,7 @@ dump_lkcd_environment_v2_v3(ulong arg)
 	lkcd_print("    dh_num_pages: ");
 	lkcd_print(BITS32() ? "%ld\n" : "%d\n", dh->dh_num_pages);
         lkcd_print(" dh_panic_string: %s%s", dh->dh_panic_string,
-		dh && dh->dh_panic_string &&
-		strstr(dh->dh_panic_string, "\n") ? "" : "\n");
+		dh && strstr(dh->dh_panic_string, "\n") ? "" : "\n");
         lkcd_print("         dh_time: %s\n",
                         strip_linefeeds(ctime(&(dh->dh_time.tv_sec))));
 

lkcd_v5.c

@@ -270,8 +270,7 @@ dump_lkcd_environment_v5(ulong arg)
 	lkcd_print("    dh_num_pages: ");
 	lkcd_print(BITS32() ? "%ld\n" : "%d\n", dh->dh_num_pages);
         lkcd_print(" dh_panic_string: %s%s", dh->dh_panic_string,
-		dh && dh->dh_panic_string &&
-		strstr(dh->dh_panic_string, "\n") ? "" : "\n");
+		dh && strstr(dh->dh_panic_string, "\n") ? "" : "\n");
         lkcd_print("         dh_time: %s\n",
                         strip_linefeeds(ctime(&(dh->dh_time.tv_sec))));
 

lkcd_v7.c

@@ -347,8 +347,7 @@ dump_lkcd_environment_v7(ulong arg)
 	lkcd_print("    dh_num_pages: ");
 	lkcd_print(BITS32() ? "%ld\n" : "%d\n", dh->dh_num_pages);
         lkcd_print(" dh_panic_string: %s%s", dh->dh_panic_string,
-		dh && dh->dh_panic_string &&
-		strstr(dh->dh_panic_string, "\n") ? "" : "\n");
+		dh && strstr(dh->dh_panic_string, "\n") ? "" : "\n");
         lkcd_print("         dh_time: %s\n",
                         strip_linefeeds(ctime(&(dh->dh_time.tv_sec))));
 

lkcd_v8.c

@@ -543,8 +543,7 @@ dump_lkcd_environment_v8(ulong arg)
 	lkcd_print("    dh_num_pages: ");
 	lkcd_print(BITS32() ? "%ld\n" : "%d\n", dh->dh_num_pages);
         lkcd_print(" dh_panic_string: %s%s", dh->dh_panic_string,
-		dh && dh->dh_panic_string &&
-		strstr(dh->dh_panic_string, "\n") ? "" : "\n");
+		dh && strstr(dh->dh_panic_string, "\n") ? "" : "\n");
 	tv.tv_sec = dh->dh_time.tv_sec;
         lkcd_print("         dh_time: %s\n",
                         strip_linefeeds(ctime(&(tv.tv_sec))));