arm: socfpga: Enabling MTD default partitions

arm: socfpga: Enabling MTD default partitions

Enabling MTD default partitions if its not defined in board
configuration file. The layout as below
 device nor0 <ff705000.spi.0>, # parts = 6
 #: name                size            offset          mask_flags
 0: u-boot              0x00100000      0x00000000      0
 1: env1                0x00040000      0x00100000      0
 2: env2                0x00040000      0x00140000      0
 3: UBI                 0x03e80000      0x00180000      0
 4: boot                0x00e80000      0x00180000      0
 5: rootfs              0x01000000      0x01000000      0

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>