pinctrl: Staticize pinconf_ops

They are not referenced outside respective driver.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Simon Arlott <simon@fire.lp0.eu>
Cc: John Crispin <blogic@openwrt.org>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>