drm/radeon/dpm: move platform caps fetching to a separate function

It's needed by by both the asic specific functions and the
extended table parser.

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/ci_dpm.c
Simple merge

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

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

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

diff --cc drivers/gpu/drm/radeon/r600_dpm.c
Simple merge

diff --cc drivers/gpu/drm/radeon/r600_dpm.h
Simple merge

diff --cc drivers/gpu/drm/radeon/rs780_dpm.c
Simple merge

diff --cc drivers/gpu/drm/radeon/rv6xx_dpm.c
Simple merge

diff --cc drivers/gpu/drm/radeon/rv770_dpm.c
Simple merge

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

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

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