Adjust irdma_prep_for_unregister() definition to avoid clang 15 warning

With clang 15, the following -Werror warning is produced:

sys/dev/irdma/icrdma.c:621:26: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
irdma_prep_for_unregister()
                         ^
                          void

This is because irdma_prep_for_unregister() is declared with a (void)
argument list, but defined with an empty argument list. Make the
definition match the declaration.

(cherry picked from commit ee6c09ac73b5eab848c66e539f8b3293a5abd7f8)