drm/nouveau: use mutex for vbios lock

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nouveau_bios.h b/drivers/gpu/drm/nouveau/nouveau_bios.h
index 68446fd..fd94bd6 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bios.h
+++ b/drivers/gpu/drm/nouveau/nouveau_bios.h
@@ -205,7 +205,7 @@
 	struct drm_device *dev;
 	struct nouveau_bios_info pub;
 
-	spinlock_t lock;
+	struct mutex lock;
 
 	uint8_t data[NV_PROM_SIZE];
 	unsigned int length;