drm: add logging for RMFB ioctl

We already have logging for ADDFB2. Add some logging for RMFB as
well.

This can be handy when trying to find out why a CRTC gets magically
disabled.

v2: make log message more explicit, add log messages to
drm_framebuffer_remove (Daniel)

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/EghsoRDcn1SJV0nxVqRCisPd7v0627yLZbBjn4A8Yg@cp3-web-048.plabs.ch