drm/fb: remove drm_fb_helper_setcolreg

This patch is against the drm-fbdevfix1 branch. It removes the
drm_fb_helper_setcolreg function. The reason is that fb_setcolreg is only
used in the case where fb_setcmap is called and no fb_ops->fb_setcmap is
used. In the drm case we always need a fb_setcmap hook to handle multiple
crtcs so we don't need a fb_setcolreg hook. Please apply.

Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>