davinci: da850 evm: sparse cleanup: make file local variables static

Without this cleanup, sparse checker reports warnings of the type:

  CHECK   arch/arm/mach-davinci/board-da850-evm.c
arch/arm/mach-davinci/board-da850-evm.c:112:22: warning: symbol 'da850_evm_nandflash_partition' was not declared. Should it be static?

The nand flash partitions and regulator supplies are used within
the EVM file and so should have been static

This patch has been boot tested on DA830 and DA850 EVMs.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>