bpf: Fix compilation warning with -Wparentheses

The kernel test robot reported compilation warnings when -Wparentheses is
added to KBUILD_CFLAGS with gcc compiler. The following is the error message:

  .../bpf-next/kernel/bpf/verifier.c: In function ‘coerce_reg_to_size_sx’:
  .../bpf-next/kernel/bpf/verifier.c:5901:14:
    error: suggest parentheses around comparison in operand of ‘==’ [-Werror=parentheses]
    if (s64_max >= 0 == s64_min >= 0) {
        ~~~~~~~~^~~~
  .../bpf-next/kernel/bpf/verifier.c: In function ‘coerce_subreg_to_size_sx’:
  .../bpf-next/kernel/bpf/verifier.c:5965:14:
    error: suggest parentheses around comparison in operand of ‘==’ [-Werror=parentheses]
    if (s32_min >= 0 == s32_max >= 0) {
        ~~~~~~~~^~~~

To fix the issue, add proper parentheses for the above '>=' condition
to silence the warning/error.

I tried a few clang compilers like clang16 and clang18 and they do not emit
such warnings with -Wparentheses.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307281133.wi0c4SqG-lkp@intel.com/
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230728055740.2284534-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Yonghong Song

kernel/bpf/core.c

@@ -1877,7 +1877,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 		case 1:
 			AX = abs((s32)DST);
 			do_div(AX, abs((s32)SRC));
-			if ((s32)DST < 0 == (s32)SRC < 0)
+			if (((s32)DST < 0) == ((s32)SRC < 0))
 				DST = (u32)AX;
 			else
 				DST = (u32)-AX;
@@ -1904,7 +1904,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 		case 1:
 			AX = abs((s32)DST);
 			do_div(AX, abs((s32)IMM));
-			if ((s32)DST < 0 == (s32)IMM < 0)
+			if (((s32)DST < 0) == ((s32)IMM < 0))
 				DST = (u32)AX;
 			else
 				DST = (u32)-AX;

kernel/bpf/verifier.c

@@ -5898,7 +5898,7 @@ static void coerce_reg_to_size_sx(struct bpf_reg_state *reg, int size)
 	s64_min = min(init_s64_max, init_s64_min);
 
 	/* both of s64_max/s64_min positive or negative */
-	if (s64_max >= 0 == s64_min >= 0) {
+	if ((s64_max >= 0) == (s64_min >= 0)) {
 		reg->smin_value = reg->s32_min_value = s64_min;
 		reg->smax_value = reg->s32_max_value = s64_max;
 		reg->umin_value = reg->u32_min_value = s64_min;
@@ -5962,7 +5962,7 @@ static void coerce_subreg_to_size_sx(struct bpf_reg_state *reg, int size)
 	s32_max = max(init_s32_max, init_s32_min);
 	s32_min = min(init_s32_max, init_s32_min);
 
-	if (s32_min >= 0 == s32_max >= 0) {
+	if ((s32_min >= 0) == (s32_max >= 0)) {
 		reg->s32_min_value = s32_min;
 		reg->s32_max_value = s32_max;
 		reg->u32_min_value = (u32)s32_min;