da850: Enable SPI Flash

The patch was already posted to the arago project,
but not yet to mainline. It allows to save environment into
the spi flash. Tested on LogiPD tmdxl138.

Signed-off-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Signed-off-by: Stefano Babic <sbabic@denx.de>
CC: Detlev Zundev <dzu@denx.de>
CC: Ben Gardiner <bengardiner@nanometrics.ca>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>