sysrq: fix ftrace help msg & doc.

Impact: update documentation and help messages

We have a conventional method of explicitly stating the
sysrq action key in a sysrq help message, so change
dump-ftrace-buffer to use that method and add it to
Documentation/sysrq.txt.
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Documentation/sysrq.txt

@@ -114,6 +114,8 @@ On all -  write a character to /proc/sysrq-trigger.  e.g.:
 
 'x'	- Used by xmon interface on ppc/powerpc platforms.
 
+'z'	- Dump the ftrace buffer
+
 '0'-'9' - Sets the console log level, controlling which kernel messages
           will be printed to your console. ('0', for example would make
           it so that only emergency messages like PANICs or OOPSes would

drivers/char/sysrq.c

@@ -283,7 +283,7 @@ static void sysrq_ftrace_dump(int key, struct tty_struct *tty)
 }
 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 	.handler	= sysrq_ftrace_dump,
-	.help_msg	= "dumpZ-ftrace-buffer",
+	.help_msg	= "dump-ftrace-buffer(Z)",
 	.action_msg	= "Dump ftrace buffer",
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };