drm: ast,cirrus,mgag200: use drm_can_sleep

these 3 were checking in_interrupt but we have situations where
calling vunmap under this could cause a BUG to be hit in
smp_call_function_many. Use the drm_can_sleep macro instead,
which should stop this path from been taken in this case.

Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ast/ast_fb.c

@@ -65,7 +65,7 @@ static void ast_dirty_update(struct ast_fbdev *afbdev,
 	 * then the BO is being moved and we should
 	 * store up the damage until later.
 	 */
-	if (!in_interrupt())
+	if (!drm_can_sleep())
 		ret = ast_bo_reserve(bo, true);
 	if (ret) {
 		if (ret != -EBUSY)

drivers/gpu/drm/cirrus/cirrus_fbdev.c

@@ -39,7 +39,7 @@ static void cirrus_dirty_update(struct cirrus_fbdev *afbdev,
 	 * then the BO is being moved and we should
 	 * store up the damage until later.
 	 */
-	if (!in_interrupt())
+	if (!drm_can_sleep())
 		ret = cirrus_bo_reserve(bo, true);
 	if (ret) {
 		if (ret != -EBUSY)

drivers/gpu/drm/mgag200/mgag200_fb.c

@@ -41,7 +41,7 @@ static void mga_dirty_update(struct mga_fbdev *mfbdev,
 	 * then the BO is being moved and we should
 	 * store up the damage until later.
 	 */
-	if (!in_interrupt())
+	if (!drm_can_sleep())
 		ret = mgag200_bo_reserve(bo, true);
 	if (ret) {
 		if (ret != -EBUSY)