drm/radeon: handle ss percentage divider properly

It's either 100 or 1000 depending on the flags in the
table.

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

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

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

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