[predicate] remove register_even_operand predicate.

- remove register_even_operand predicate. The even-odd pairs of register allocation in rv32_zpsf is handled by riscv_hard_regno_mode_ok hook now

gcc/config/riscv/predicates.md

@@ -213,24 +213,6 @@
   return riscv_gpr_save_operation_p (op);
 })
 
-(define_predicate "register_even_operand"
-  (match_operand 0 "register_operand")
-{
-  if (GET_CODE (op) == SUBREG)
-    op = SUBREG_REG (op); /* Possibly a MEM */
-
-  if (!REG_P (op))
-    return false;
-
-  if (REGNO (op) >= FIRST_PSEUDO_REGISTER)
-    return true;
-
-  return ((!TARGET_64BIT
-	   && GP_REG_P (REGNO (op))
-	   && (REGNO (op) & 1) == 0)
-	  || (TARGET_64BIT && GP_REG_P (REGNO (op))));
-})
-
 (define_predicate "imm2u_operand"
   (and (match_operand 0 "const_int_operand")
        (match_test "satisfies_constraint_u02 (op)")))