pinctrl: spear/plgpio: Staticize spear310_o2p

'spear310_o2p' is referenced only in this file.
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/spear/pinctrl-plgpio.c

@@ -441,7 +441,7 @@ static int spear310_p2o(int pin)
 	return offset;
 }
 
-int spear310_o2p(int offset)
+static int spear310_o2p(int offset)
 {
 	if (offset <= 3)
 		return 101 - offset;