media: rkisp1: debug: Update max register name length

Update the maximum register name length to match all the registers being
printed. This helps getting a consistent alignment of register dumps
when concatenating multiple debugfs files.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>