Adjust function definitions in netipsec's key.c to avoid clang 15 warnings
With clang 15, the following -Werror warnings are produced:
sys/netipsec/key.c:6432:15: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] key_getcomb_ah() ^ void sys/netipsec/key.c:6489:19: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] key_getcomb_ipcomp() ^ void
This is because key_getcomb_ah() and key_getcomb_ipcomp() are declared
with (void) argument lists, but defined with empty argument lists. Make
the definitions match the declarations.
MFC after: 3 days
(cherry picked from commit 8bd2887be5105010e73fc35ddd25021e186811b8)