drm: Provide PCI module-init macros

Provide helper macros to register PCI-based DRM drivers. The new
macros behave like module_pci_driver() with an additional test if
DRM modesetting has been enabled.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211222082831.196562-2-javierm@redhat.com