ARM/etm/sysrq: fix inconstistent help message of sysrq key

Currently help message of /proc/sysrq-trigger highlights its
upper-case characters, like below:

      SysRq : HELP : loglevel(0-9) reBoot Crash terminate-all-tasks(E)
      memory-full-oom-kill(F) kill-all-tasks(I) ...

this would confuse user trigger sysrq by upper-case character, which is
inconsistent with the real lower-case character registed key.

This inconsistent help message will also lead more confused when
26 upper-case letters put into use in future.

This patch fix arm etm sysrq key: "etm-buffer-dump(v)"
(This patch also add "-" to separate each sysrq key help word,
instead of spaces)

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/kernel/etm.c

@@ -254,7 +254,7 @@ static void sysrq_etm_dump(int key)
 
 static struct sysrq_key_op sysrq_etm_op = {
 	.handler = sysrq_etm_dump,
-	.help_msg = "ETM buffer dump",
+	.help_msg = "etm-buffer-dump(v)",
 	.action_msg = "etm",
 };