mmc: sdhci-sirf: let device core setup the default pin configuration

With device core now able to setup the default pin configuration, the
call to devm_pinctrl_get_select_default can be removed. And the pin
configuration code based on the deprecated Samsung specific gpio
bindings is also removed.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Chris Ball <cjb@laptop.org>