drm/client: Inline drm_client_buffer_addfb() and _rmfb()

drm/client: Inline drm_client_buffer_addfb() and _rmfb()

Creating and deleting a client buffer always creates and deletes
the underlying DRM framebuffer. Inline the helper functions into
their callers.

With the _addfb code being inlined into drm_client_buffer_create(),
clean up the function's error rollback to release the framebuffer's
handle and GEM buffer object as needed.

Move the _rmfb code into drm_client_buffer_delete() rather than its
current location in drm_client_framebuffer_delete(). The former is
now the inverse of drm_client_buffer_create(). Makes no difference
for cleaning up. Also prepares for the removal of
drm_client_framebuffer_delete().

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/20251027121042.143588-4-tzimmermann@suse.de