rfkill: introduce RFKILL_STATE_MAX

While it is interesting to not add last-enum-markers because it allows gcc
to warn us of switch() statements missing a valid state, we really should
be handling memory corruption on a rfkill state with default clauses,
anyway.

So add RFKILL_STATE_MAX and use it where applicable.  It makes for safer
code in the long run.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/linux/rfkill.h b/include/linux/rfkill.h
index e92d8e9..4cd64b0 100644
--- a/include/linux/rfkill.h
+++ b/include/linux/rfkill.h
@@ -49,6 +49,7 @@
 	RFKILL_STATE_SOFT_BLOCKED = 0,	/* Radio output blocked */
 	RFKILL_STATE_UNBLOCKED    = 1,	/* Radio output allowed */
 	RFKILL_STATE_HARD_BLOCKED = 2,	/* Output blocked, non-overrideable */
+	RFKILL_STATE_MAX,		/* marker for last valid state */
 };
 
 /*