drm/radeon/dpm: add pre/post_set_power_state callback (BTC)

This properly implemented dynamic state adjustment by
using a working copy of the requested and current
power states.

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/cypress_dpm.h
Simple merge

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

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