ath6kl: Use cc-disable-warning to disable -Wdangling-pointer

Clang does not support this option so the build fails:

  error: unknown warning option '-Wno-dangling-pointer' [-Werror,-Wunknown-warning-option]

Use cc-disable-warning so that the option is only added when it is
supported.

Fixes: bd1d129d

 ("wifi: ath6k: silence false positive -Wno-dangling-pointer warning on GCC 12")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20220524145655.869822-1-nathan@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>