ARM: davinci: da850 evm: fix const qualifier placement

const qualifier was misplaced in couple of definitions.
This fixes the sparse error:

  CHECK   arch/arm/mach-davinci/board-mityomapl138.c
arch/arm/mach-davinci/board-da850-evm.c:404:19: error: Just how const do you want this type to be?
arch/arm/mach-davinci/board-da850-evm.c:568:19: error: Just how const do you want this type to be?

Signed-off-by: Sekhar Nori <nsekhar@ti.com>