media: atmel: move microchip_csi2dc to dedicated microchip platform

The Atmel ISC will be moved to staging thus the atmel platform will only
have the ISI driver.
The new media-controller converted ISC driver will be placed inside a
dedicated microchip platform directory.
It is then natural to have the microchip-csi2dc moved to this new platform
directory.
The next step is to add the Microchip ISC driver to the new platform
directory and reside together with the Microchip CSI2DC driver.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>