media: ov5640: Add pixel rate to modes

Add to each mode supported by the sensor the ideal pixel rate, as
defined by Table 2.1 in the chip manual.

The ideal pixel rate will be used to compute the MIPI CSI-2 clock tree.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Adam Ford <aford173@gmail.com> #imx8mm-beacon-kit
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>