staging: greybus: Fix uninitialized scalar variable

In the "gb_tty_set_termios" function the "newline" variable is declared
but not initialized. So the "flow_control" member is not initialized and
the OR / AND operations with itself results in an undefined value in
this member.

The purpose of the code is to set the flow control type, so remove the
OR / AND self operator and set the value directly.

Addresses-Coverity-ID: 1374016 ("Uninitialized scalar variable")
Fixes: e55c2520

 ("greybus: uart: Handle CRTSCTS flag in termios")
Signed-off-by: Oscar Carter <oscar.carter@gmx.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200510101426.23631-1-oscar.carter@gmx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>