[PATCH] Char: mxser_new, do not null driver_data

driver_data are initialzed to NULL from tty layer, no need to do it in the
driver.  In this case it cases oops, since driver_data may be NULL for a short
while for another closing process.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: <osv@javad.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>