drm/tegra: dc: Remove redundant spinlock

The spinlock is only used to serialize accesses to the DC_CMD_INT_MASK
register. However, this register is accesses either with interrupts
masked (in tegra_crtc_atomic_enable()) or protected by the vbl_lock and
vblank_time_lock spinlocks of the DRM device. Therefore, these accesses
don't need any extra serialization and the lock can be removed.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.h

@@ -71,7 +71,6 @@ struct tegra_dc {
 	struct host1x_client client;
 	struct host1x_syncpt *syncpt;
 	struct device *dev;
-	spinlock_t lock;
 
 	struct drm_crtc base;
 	unsigned int powergate;