pinctrl: mediatek: mark dummy helpers as 'static inline'

mtk_eint_set_debounce and mtk_eint_find_irq are defined as stub functions
in a header file, but without marking them as 'static inline', we get
a copy for each file that includes the header:

drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.o: In function `mtk_eint_set_debounce':
pinctrl-mtk-common-v2.c:(.text+0x134): multiple definition of `mtk_eint_set_debounce'
drivers/pinctrl/mediatek/pinctrl-moore.o:pinctrl-moore.c:(.text+0x7d0): first defined here
drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.o: In function `mtk_eint_find_irq':
pinctrl-mtk-common-v2.c:(.text+0x13c): multiple definition of `mtk_eint_find_irq'

Fixes: e46df235b4e6 ("pinctrl: mediatek: refactor EINT related code for all MediaTek pinctrl can fit")
Signed-off-by: Arnd Bergmann <[e-mail]>
Acked-by: Sean Wang <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/mediatek/mtk-eint.h

···
 	return -EOPNOTSUPP;
 }
 
-int mtk_eint_set_debounce(struct mtk_eint *eint, unsigned long eint_n,
+static inline int mtk_eint_set_debounce(struct mtk_eint *eint, unsigned long eint_n,
 			  unsigned int debounce)
 {
 	return -EOPNOTSUPP;
 }
 
-int mtk_eint_find_irq(struct mtk_eint *eint, unsigned long eint_n)
+static inline int mtk_eint_find_irq(struct mtk_eint *eint, unsigned long eint_n)
 {
 	return -EOPNOTSUPP;
 }