media: i2c: imx290: Specify HMAX values in decimal

The HMAX value specifies the total line length in pixels. It's thus more
readable in decimal than hexadecimal. Fix it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>