mfd: wm8994: Remove unneeded check for JACKDET

The jack detection code holds runtime PM references when required so
there is no need for suspend to do any checks.

Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>