drivers: char: ipmi: Replaced kmalloc and strcpy with kstrdup

Replaced calls to kmalloc followed by strcpy with a sincle call to
kstrdup.  Patch found using coccinelle.

Signed-off-by: Alexandru Gheorghiu <gheorghiuandru@gmail.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>