drm/radeon: drop use of drmP.h (1/2)

Drop use of drmP.h in all .c files named radeon*c.
To ease review a little drmP.h removal was divided in two commits.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: "David (ChunMing) Zhou" <David1.Zhou@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190608080241.4958-7-sam@ravnborg.org