MLK-16062-5: dts: i.MX8QM arm2 default support 4 mipi sensors

MLK-16062-5: dts: i.MX8QM arm2 default support 4 mipi sensors

i.MX8QM can support 4 camera sensors or 8 camera sensors.

For eight sensors case, it must need all eight sensors on board,
and for four sensors case, it must need all four sensors on board,
otherwise all mipi sensor can't work.

Four mipi sensors case is more popular than eight sensors.
so change to default support four sensors.

Signed-off-by: Sandor Yu <Sandor.yu@nxp.com>