[PATCH] zd1201: Possible NULL dereference

If we enter the if(!zd) and set free to 1, we dereference zd in the exit
code.

Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>