[PATCH] Char: mxser_new, correct fail paths

Resources were not released in some fail paths.  Correct this behaviour by
implementing function and calling it when something fails.

Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>