fbdev/intelfb: Remove driver

From looking at the PCI IDs, every device supported by intelfb is
also supported by i915. Anyone still using intelfb should please
move on to i915, which does everything intelfb does but better.

Removing intelfb is motivated by the driver's excessive use of the
global screen_info state. The state belongs to architecture and
firmware code; device drivers should not attempt to access it. But
fixing intelfb would require a significant change in the driver's
probing logic. As intelfb has been obsolete for nearly 2 decades,
it is probably not worth the effort. Let's just remove it. Also
remove the related documentation.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Maik Broemme <mbroemme@libmpq.org>
Signed-off-by: Helge Deller <deller@gmx.de>