tty_audit: use kzalloc() in tty_audit_buf_alloc()

tty_audit_buf_alloc() manually erases most of the entries after
kmalloc(). So use kzalloc() and remove the manual sets to zero.

That way, we are sure that we do not omit anything.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230621101611.10580-3-jirislaby@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>