Revert "tty/serial/8250: use mctrl_gpio helpers"

Serial console is broken in v4.8-rcX. Mika and I independently bisected down to
commit 4ef03d32 ("tty/serial/8250: use mctrl_gpio helpers").

Since neither author nor anyone else didn't propose a solution we better revert
it for now.

This reverts commit 4ef03d32

.

Link: https://lkml.kernel.org/r/20160809130229.GN1729@lahna.fi.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>