drm/nouveau/bios: pointers beyond end of first image need special handling

Makes common the code that was previously used by the PMU table parsing,
as it appears other tables need this too.

Not much of an idea what this is all about...

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/subdev/bios.h

@@ -7,6 +7,9 @@ struct nvkm_bios {
 	u32 size;
 	u8 *data;
 
+	u32 image0_size;
+	u32 imaged_addr;
+
 	u32 bmp_offset;
 	u32 bit_offset;