mfd: Test for jack detection when deciding if wm8994 should suspend

The jack detection on WM1811 is often required during system suspend, add
it as another check when deciding if we should suspend.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@vger.kernel.org
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>