commit a1efd14a upstream.

Apparently i830 and i845 cannot handle any stride that is not a multiple
of 256, unlike their brethren which do support 64 byte aligned strides.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>