pinctrl: artpec6: Make two functions static

Fix sparse warnings:

drivers/pinctrl/pinctrl-artpec6.c:691:5: warning:
 symbol 'artpec6_pmx_enable' was not declared. Should it be static?
drivers/pinctrl/pinctrl-artpec6.c:705:6: warning:
 symbol 'artpec6_pmx_disable' was not declared. Should it be static?
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-artpec6.c

@@ -688,7 +688,8 @@ static void artpec6_pmx_select_func(struct pinctrl_dev *pctldev,
 	}
 }
 
-int artpec6_pmx_enable(struct pinctrl_dev *pctldev, unsigned int function,
+static int artpec6_pmx_enable(struct pinctrl_dev *pctldev,
+			      unsigned int function,
 			      unsigned int group)
 {
 	struct artpec6_pmx *pmx = pinctrl_dev_get_drvdata(pctldev);
@@ -702,7 +703,8 @@ int artpec6_pmx_enable(struct pinctrl_dev *pctldev, unsigned int function,
 	return 0;
 }
 
-void artpec6_pmx_disable(struct pinctrl_dev *pctldev, unsigned int function,
+static void artpec6_pmx_disable(struct pinctrl_dev *pctldev,
+				unsigned int function,
 				unsigned int group)
 {
 	struct artpec6_pmx *pmx = pinctrl_dev_get_drvdata(pctldev);