drm/atomic: Spell CRTC consistently

CRTC is an abbreviation and should be all caps in prose. Update all
kerneldoc comments to use a consistent spelling.

v2: remove hunk unrelated to the CRTC spelling fixes

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191206135336.2084564-2-thierry.reding@gmail.com