libkmod: silence autological compare warning

libkmod: silence autological compare warning

Clang will detect that the enum cannot be zero, thus triggering a
warning. Since this is an external (public API) function, the end-user
can provide any input so we want to keep the check.

Note: include the pragmas in a if defined(__clang__) guard, otherwise
we'll trigger -Wunknown_pragma which will become an error in CI and
developer builds.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/172
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>