drm/mgag200,ast,cirrus: fix regression with drm_can_sleep conversion

I totally sign inverted my way out of this one.

Cc: stable@vger.kernel.org
Reported-by: "Sabrina Dubroca" <sd@queasysnail.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --cc drivers/gpu/drm/ast/ast_fb.c
Simple merge

diff --cc drivers/gpu/drm/cirrus/cirrus_fbdev.c
Simple merge

diff --cc drivers/gpu/drm/mgag200/mgag200_fb.c
Simple merge