da850evm: setup NAND support under CONFIG_USE_NAND

da850evm: setup NAND support under CONFIG_USE_NAND

The current da850evm config is missing the pieces for NAND support that can be
found in Sandeep's u-boot-davinci tree [1].

This patch adds NAND support in the spirit of the support in the u-boot-davinci
tree where NAND support for the da850evm can be enabled by putting a single
'#define CONFIG_USE_NAND' at the top of the include/configs/da850evm.h file.

[1] http://arago-project.org/git/people/?p=sandeep/u-boot-davinci.git;a=tree

Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>