UBI: Add UBI command support

UBI: Add UBI command support

This patch adds these UBI commands:

ubi part [nand|onenand] [part] - Show or set current partition
ubi info [l[ayout]] -Display volume and UBI layout information
ubi create[vol] volume [size] [type] - Create volume name with size
ubi write[vol] address volume size - Write volume from address with size
ubi read[vol] address volume [size] - Read volume to address with size
ubi remove[vol] volume - Remove volume

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Stefan Roese <sr@denx.de>