media: i2c: imx290: Fix the pixel rate at 148.5Mpix/s

The datasheet lists the link frequency changes between
1080p and 720p modes. This is correct that the link frequency
changes as measured on an oscilloscope.

Link frequency is not necessarily the same as pixel rate.

The datasheet gives standard configurations for 1080p and 720p
modes at a number of frame rates.
Looking at the 1080p mode it gives:
HMAX = 0x898 = 2200
VMAX = 0x465 = 1125
2200 * 1125 * 60fps = 148.5MPix/s

Looking at the 720p mode it gives:
HMAX = 0xce4 = 3300
VMAX = 0x2ee = 750
3300 * 750 * 60fps = 148.5Mpix/s

This driver currently scales the pixel rate proportionally to the
link frequency, however the above shows that this is not the
correct thing to do, and currently all frame rate and exposure
calculations give incorrect results.

Correctly report the pixel rate as being 148.5MPix/s under any
mode.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>