drm/radeon/dpm/btc: restructure code

Needed to properly handle dynamic state adjustment.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --cc drivers/gpu/drm/radeon/btc_dpm.c
Simple merge

diff --cc drivers/gpu/drm/radeon/btc_dpm.h
Simple merge

diff --cc drivers/gpu/drm/radeon/ni_dpm.c
Simple merge