linuxkpi: clean up stray pctrie_iter_reset

This removes an extraneous pctrie_iter_reset before returning.
This is not needed as it simply clears a local variable that
will get cleaned up anyway as we immediately return from the
function.

MFC after: 1 week
Sponsored by: NVIDIA
Reviewed by: alc
Differential Revision: https://reviews.freebsd.org/D54153