The datasheet specifies the upper four bits are reserved.
Testing on real hardware shows that these bits can indeed be nonzero.
Signed-off-by: NEmil Lenngren <emil.lenngren@gmail.com>
Reviewed-by: NBoris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>