gpio: davinci: use {readl|writel}_relaxed() instead of __raw_*

This patch replaces the __raw_readl/writel with
{readl|writel}_relaxed(), Altough the code runs on ARMv5
based SOCs, changing this will help using code for other
use cases (like with big-endian machines).

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>