ARM: davinci: use is IS_ENABLED macro

This patches replaces #if defined() by IS_ENABLED macro, which provides
better readability.

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>