bpf: Fix compilation warning with -Wparentheses

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>