pinctrl: fix compile error if not select PINMUX support

The pinctrl_register_mappings is defined in core.c, so change the dependent
macro from CONFIG_MUX to CONFIG_PINCTRL.

The compile error message is:
drivers/pinctrl/core.c:886: error: redefinition of 'pinctrl_register_mappings'
include/linux/pinctrl/machine.h:160: note: previous definition of 'pinctrl_register_mappings' was here
make[2]: *** [drivers/pinctrl/core.o] Error 1
make[1]: *** [drivers/pinctrl] Error 2
make: *** [drivers] Error 2

Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: Dong Aisheng

include/linux/pinctrl/machine.h

@@ -148,7 +148,7 @@ struct pinctrl_map {
 #define PIN_MAP_CONFIGS_GROUP_HOG_DEFAULT(dev, grp, cfgs)		\
 	PIN_MAP_CONFIGS_GROUP(dev, PINCTRL_STATE_DEFAULT, dev, grp, cfgs)
 
-#ifdef CONFIG_PINMUX
+#ifdef CONFIG_PINCTRL
 
 extern int pinctrl_register_mappings(struct pinctrl_map const *map,
 				unsigned num_maps);