arm: socfpga: sr1500: Enable ubiload console command

arm: socfpga: sr1500: Enable ubiload console command

Enabling ubiload command to load kernel image and
device tree from mtd part labeled "UBI". ubiload
command will search the file from directory /boot.

Signed-off-by: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Dinh Nguyen <dinh.linux@gmail.com>
Cc: Pavel Machek <pavel@denx.de>
Cc: Marek Vasut <marex@denx.de>
Cc: Stefan Roese <sr@denx.de>