MAINTAINERS: Broaden scope of simpledrm entry

There will be more DRM drivers for firmware-provided framebuffers. Use
the existing entry for simpledrm instead of adding a new one for each
driver. Also add DRM's aperture helpers, which are part of the driver's
infrastructure.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Javier Martinez Canillas <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

MAINTAINERS

···
 F:	drivers/gpu/drm/savage/
 F:	include/uapi/drm/savage_drm.h
 
-DRM DRIVER FOR SIMPLE FRAMEBUFFERS
+DRM DRIVER FOR FIRMWARE FRAMEBUFFERS
 M:	Thomas Zimmermann <[e-mail]>
 M:	Javier Martinez Canillas <[e-mail]>
 L:	[e-mail]
 S:	Maintained
 T:	git git://anongit.freedesktop.org/drm/drm-misc
+F:	drivers/gpu/drm/drm_aperture.c
 F:	drivers/gpu/drm/tiny/simpledrm.c
+F:	include/drm/drm_aperture.h
 
 DRM DRIVER FOR SIS VIDEO CARDS
 S:	Orphan / Obsolete