crisv10: use flags from tty_port

First, remove STD_FLAGS as the value, or its subvalues
(ASYNC_BOOT_AUTOCONF | ASYNC_SKIP_TEST) is not tested anywhere --
there is no point to initialize flags to that. Second, use flags
member from tty_port when we have it now. So that we do not waste
space.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>