drm/sysfb: Split source file

Split drm_sysfb_helper.c into two source files. There's now one
source file for the mode-setting pipeline and one source file for
module meta data. Prepares for adding additional source code to
sysfb helpers.

v2:
- fix typo in commit message (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250410083834.10810-2-tzimmermann@suse.de