driver core: platform: Export platform_get_irq_optional()

This function can be used by modules, so it needs to be exported.
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/platform.c

@@ -213,6 +213,7 @@ int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
 {
 	return __platform_get_irq(dev, num);
 }
+EXPORT_SYMBOL_GPL(platform_get_irq_optional);
 
 /**
  * platform_irq_count - Count the number of IRQs a platform device uses