can: unify identifiers to ensure unique include processing

Armin pointed me to the fact that the identifier which is used to ensure the
unique include processing in lunux/include/uapi/linux/can.h is CAN_H.
This clashed with his own source as includes from libraries and APIs should
use an underscore '_' at the identifier start.

This patch fixes the protection identifiers in all CAN relavant includes.

Reported-by: Armin Burchardt <armin@uni-bremen.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

include/linux/can/platform/mcp251x.h

@@ -1,5 +1,5 @@
-#ifndef __CAN_PLATFORM_MCP251X_H__
-#define __CAN_PLATFORM_MCP251X_H__
+#ifndef _CAN_PLATFORM_MCP251X_H
+#define _CAN_PLATFORM_MCP251X_H
 
 /*
  *
@@ -18,4 +18,4 @@ struct mcp251x_platform_data {
 	unsigned long oscillator_frequency;
 };
 
-#endif /* __CAN_PLATFORM_MCP251X_H__ */
+#endif /* !_CAN_PLATFORM_MCP251X_H */