ARM: davinci: make file local variables static

Make file local variables static in mach-davinci.
This fixes sparse warnings of the form:

arch/arm/mach-davinci/dm355.c:863:27: warning: symbol 'dm355_venc_pdata' was not declared. Should it be static?

Cc: Prabhakar Lad <prabhakar.csengg@gmail.com>
Acked-by: Prabhakar Lad <prabhakar.csengg@gmail.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>