media: atmel-isc: Rework the format list

To improve the readability of code, split the format array into two,
one for the format description, other for the register configuration.
Meanwhile, add the flag member to indicate the format can be achieved
from the sensor or be produced by the controller, and rename members
related to the register configuration.

Also add more formats support: GREY, ARGB444, ARGB555 and ARGB32.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>