serial: samsung: Restore IRQ mask during noirq resume

This closes a window where the system may hang in resume as soon as the
UART interrupt is enabled and before the mask is restored. The hang occurs
because the driver can't handle IRQs it thinks are masked.

Signed-off-by: Michael Spang <spang@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>