drm/vc4: crtc: Provide a CRTC name

It's fairly hard to figure out the instance of the CRTC affected by an
atomic change using the default name.

Since we can provide our own to the CRTC initialization functions, let's
do so to make the debugging sessions easier.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20221123-rpi-kunit-tests-v1-20-051a0bb60a16@cerno.tech