[PATCH] gpio: Fix the no return statement warning for gpiochip_populate_parent_fwspec_twocell/fourcell()

[Kevin Hao <haokexin@xxxxxxxxx>]

In commit 242587616710 ("gpiolib: Add support for the irqdomain which
doesn't use irq_fwspec as arg") we have changed the return type of
gpiochip_populate_parent_fwspec_twocell/fourcell() from void to void *,
but forgot to add a return statement for these two dummy functions.
Add "return NULL" to fix the build warnings.

Reported-by: kbuild test robot <lkp@xxxxxxxxx>
Signed-off-by: Kevin Hao <haokexin@xxxxxxxxx>
---
 include/linux/gpio/driver.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index ea6e615ad7fc..18350f274905 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -549,12 +549,14 @@ static inline void *gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *ch
 						    unsigned int parent_hwirq,
 						    unsigned int parent_type)
 {
+	return NULL;
 }
 
 static inline void *gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *chip,
 						     unsigned int parent_hwirq,
 						     unsigned int parent_type)
 {
+	return NULL;
 }
 
 #endif /* CONFIG_IRQ_DOMAIN_HIERARCHY */
-- 
2.14.4