Adjust check_struct_sizes() definition to avoid clang 15 warning

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

sys/dev/smartpqi/smartpqi_helper.c:374:19: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
check_struct_sizes()
                  ^
                   void

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

MFC after: 3 days