media: i2c: max9271: Add header include guards to max9271.h

Protect against multiple inclusions of the max9271.h header with include
guards.

Link: https://lore.kernel.org/linux-media/[e-mail]
Signed-off-by: Laurent Pinchart <[e-mail]>
Reviewed-by: Kieran Bingham <[e-mail]>
Reviewed-by: Jacopo Mondi <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/i2c/max9271.h

···
  * Copyright (C) 2015 Cogent Embedded, Inc.
  */
 
+#ifndef __MEDIA_I2C_MAX9271_H__
+#define __MEDIA_I2C_MAX9271_H__
+
 #include <linux/i2c.h>
 
 #define MAX9271_DEFAULT_ADDR	0x40
···
  * Return 0 on success or a negative error code on failure
  */
 int max9271_set_translation(struct max9271_device *dev, u8 source, u8 dest);
+
+#endif /* __MEDIA_I2C_MAX9271_H__ */