drm: drop commented out code and preceding comment

r100_gpu_init() was dropped in 90aca4d2 ("drm/radeon/kms: simplify &
improve GPU reset V2") but here it was only commented out.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>