x86: Include stdbool.h in interrupt header

This makes use of a 'bool' type, so include the required header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/include/asm/interrupt.h b/arch/x86/include/asm/interrupt.h
index e23fb2c..c689fc2 100644
--- a/arch/x86/include/asm/interrupt.h
+++ b/arch/x86/include/asm/interrupt.h
@@ -10,6 +10,7 @@
 #ifndef __ASM_INTERRUPT_H_
 #define __ASM_INTERRUPT_H_ 1
 
+#include <stdbool.h>
 #include <asm/types.h>
 
 #define SYS_NUM_IRQS	16