[patch 1/2] kernel/audit.c: warning fix

kernel/audit.c: In function 'audit_log_start':
kernel/audit.c:1133: warning: 'serial' may be used uninitialized in this function

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>