drm/nv50: prevent multiple init tables being parsed at the same time

With DVI and DP plugged, the DVI clock change interrupts being run can
cause DP link training to fail.  This adds a spinlock around init table
parsing to prevent this.

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 058e98c..68446fd 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bios.h
+++ b/drivers/gpu/drm/nouveau/nouveau_bios.h
@@ -205,6 +205,8 @@
 	struct drm_device *dev;
 	struct nouveau_bios_info pub;
 
+	spinlock_t lock;
+
 	uint8_t data[NV_PROM_SIZE];
 	unsigned int length;
 	bool execute;