[media] tc358743: Do not read number of CSI lanes in use from chip

The number of CSI lanes that should be used is set to the CSI_CONTROL
register by indirectly writing to the CSI_CONFW register. When the
number of lanes is read back from the CSI_CONTROL register the value
is usually correct, but we have seen that it suddenly is 1 for a short
moment before the correct value is restored again.

Toshiba have not figured out why that happen, but we have found it
safer to store the value in the driver.

Signed-off-by: Mats Randgaard <matrandg@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>