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

Whilst the datasheet lists the link frequency changing between
1080p and 720p modes, reality is that with the default blanking
we have
(1920 + 280) * (1080 + 45) * 60fps = 148.5MPix/s
and
(1280 + 2020) * (720 + 30) * 60fps = 148.5MPix/s
and this reflects reality whether in 10 or 12 bit readout modes.

How this relates to link frequency is unclear as it differs
from the datasheet, but all exposure and frame rate calcs need
the pixel rate to be correct, so make it so.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>