GPIO: gpio-dwapb: Change readl&writel to dwapb_read&dwapb_write

This patch replaces 'readl&writel' with 'dwapb_read&dwapb_write'.

Reviewed-by: Shevchenko, Andriy <andriy.shevchenko@intel.com>
Signed-off-by: Weike Chen <alvin.chen@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>