matroxfb: set FBINFO_READS_FAST

Set FBINFO_READS_FAST so that the console code uses scrolling instead of
rewriting. This improves scrolling speed.

A time to do ls -la /usr/bin:
	original patched
32bpp	5.4	3.6
24bpp	5.1	3.0
16bpp	4.9	2.5
8bpp	4.9	2.0

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>