arm: plat-orion: convert the registration of the xor1 engine to the single driver

Instead of registering one 'mv_xor_shared' device for the XOR engine,
and then two 'mv_xor' devices for the XOR channels, pass the channels
properties as platform_data for the main 'mv_xor_shared' device.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>