drm/radeon: use true, false for bool variable in evergreen.c

Fixes coccicheck warning:

drivers/gpu/drm/radeon/evergreen.c:4948:2-15: WARNING: Assignment of 0/1 to bool variable
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: Nzhengbin <zhengbin13@huawei.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/evergreen.c

@@ -4945,7 +4945,7 @@ static void evergreen_uvd_init(struct radeon_device *rdev)
 		 * there. So it is pointless to try to go through that code
 		 * hence why we disable uvd here.
 		 */
-		rdev->has_uvd = 0;
+		rdev->has_uvd = false;
 		return;
 	}
 	rdev->ring[R600_RING_TYPE_UVD_INDEX].ring_obj = NULL;