x86: Fix i8259 ifdef include guard

When building U-Boot with clang, it notices that the i8259.h include
guard does not work correctly due to a typo. Fix it.

Signed-off-by: Alistair Delva <adelva@google.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/include/asm/i8259.h b/arch/x86/include/asm/i8259.h
index b73052a..90f2d38 100644
--- a/arch/x86/include/asm/i8259.h
+++ b/arch/x86/include/asm/i8259.h
@@ -7,7 +7,7 @@
 /* i8259.h i8259 PIC Registers */
 
 #ifndef _ASMI386_I8259_H_
-#define _ASMI386_I8959_H_
+#define _ASMI386_I8259_H_
 
 /* PIC I/O mapped registers */
 #define IRR		0x0	/* Interrupt Request Register */
@@ -73,4 +73,4 @@
 
 int i8259_init(void);
 
-#endif /* _ASMI386_I8959_H_ */
+#endif /* _ASMI386_I8259_H_ */