irqdomain: Include internals.h for function prototypes

irq_domain_debugfs_init() is defined in irqdomain.c, but the
declaration is in a header that is not included here:

kernel/irq/irqdomain.c:1965:13: error: no previous prototype for 'irq_domain_debugfs_init' [-Werror=missing-prototypes]

Signed-off-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

kernel/irq/irqdomain.c

···
 #endif	/* CONFIG_IRQ_DOMAIN_HIERARCHY */
 
 #ifdef CONFIG_GENERIC_IRQ_DEBUGFS
+#include "internals.h"
+
 static struct dentry *domain_dir;
 
 static void