Adjust function definitions in kern_resource.c to avoid clang 15 warnings

Adjust function definitions in kern_resource.c to avoid clang 15 warnings

With clang 15, the following -Werror warnings are produced:

    sys/kern/kern_resource.c:1212:10: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
    lim_alloc()
             ^
              void
    sys/kern/kern_resource.c:1365:11: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
    uihashinit()
              ^
               void

This is because lim_alloc() and uihashinit() 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 f2eb09b089bcdf546ed3fd4c2c59d9df02c585d8)