shader_jit_x64: Fix conditional evaluation extended-bit hazard

The unit test seems to have identified a bug in the x64 jit too. The x64
jit was doing 32-bit comparisons despite the condition flags being 8-bit
values and is sensitive to garbage being in the upper 24 bits of the
register. This is fixed by using the proper 8-bit register types rather
than the 32-bit ones(`eax,`ebx` -> `al`, `bl`).

src/video_core/shader/shader_jit_x64_compiler.cpp

@@ -401,29 +401,29 @@ void JitShader::Compile_EvaluateCondition(Instruction instr) {
     // Note: NXOR is used below to check for equality
     switch (instr.flow_control.op) {
     case Instruction::FlowControlType::Or:
-        mov(eax, COND0);
-        mov(ebx, COND1);
-        xor_(eax, (instr.flow_control.refx.Value() ^ 1));
-        xor_(ebx, (instr.flow_control.refy.Value() ^ 1));
-        or_(eax, ebx);
+        mov(al, COND0.cvt8());
+        mov(bl, COND1.cvt8());
+        xor_(al, (instr.flow_control.refx.Value() ^ 1));
+        xor_(bl, (instr.flow_control.refy.Value() ^ 1));
+        or_(al, bl);
         break;
 
     case Instruction::FlowControlType::And:
-        mov(eax, COND0);
-        mov(ebx, COND1);
-        xor_(eax, (instr.flow_control.refx.Value() ^ 1));
-        xor_(ebx, (instr.flow_control.refy.Value() ^ 1));
-        and_(eax, ebx);
+        mov(al, COND0);
+        mov(bl, COND1);
+        xor_(al, (instr.flow_control.refx.Value() ^ 1));
+        xor_(bl, (instr.flow_control.refy.Value() ^ 1));
+        and_(al, bl);
         break;
 
     case Instruction::FlowControlType::JustX:
-        mov(eax, COND0);
-        xor_(eax, (instr.flow_control.refx.Value() ^ 1));
+        mov(al, COND0);
+        xor_(al, (instr.flow_control.refx.Value() ^ 1));
         break;
 
     case Instruction::FlowControlType::JustY:
-        mov(eax, COND1);
-        xor_(eax, (instr.flow_control.refy.Value() ^ 1));
+        mov(al, COND1);
+        xor_(al, (instr.flow_control.refy.Value() ^ 1));
         break;
     }
 }