[BHND/PMU] Correct shift of bits in BHND_PMU_SET_BITS macro

The purpose of BHND_PMU_{GET,SET}_BITS macro is to transform values from/into
register format. SET macro shifts value to left and applies filter mask.
GET macro applies filter mask and then shifts value to right.

Reviewed by: landonf, adrian (mentor)
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D7721