gpio: stubs in headers should be inline

Fixes: fdd61a01 ("gpio: Add support for hierarchical IRQ domains")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20190816213812.40a130db@canb.auug.org.auSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/gpio/driver.h

@@ -543,14 +543,14 @@ void gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *chip,
 
 #else
 
-static void gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *chip,
+static inline void gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *chip,
 						    struct irq_fwspec *fwspec,
 						    unsigned int parent_hwirq,
 						    unsigned int parent_type)
 {
 }
 
-static void gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *chip,
+static inline void gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *chip,
 						     struct irq_fwspec *fwspec,
 						     unsigned int parent_hwirq,
 						     unsigned int parent_type)