drm/client: Create client buffers with drm_client_buffer_create_dumb()

drm/client: Create client buffers with drm_client_buffer_create_dumb()

Rename drm_client_framebuffer_create() to drm_client_buffer_create_dump()
and adapt callers. The new name reflects the function's purpose. Using
dumb buffers is the easiest way for creating a GEM buffer in a drivers-
independent way.

There's also drm_client_buffer_create(), which creates the client buffer
from a preexisting buffer object. This helper can be exported for drivers
that create their own GEM buffer object.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Tested-by: Francesco Valla <francesco@valla.it>
Link: https://patch.msgid.link/20251027121042.143588-7-tzimmermann@suse.de