mfd: wm8994: Fix unbalanced calls to regulator_bulk_disable()

When runtime PM is enabled, regulators are being controlled by the
driver's suspend and resume callbacks. They are also unconditionally
enabled at driver's probe(), and disabled in remove() functions. Add
more calls to runtime PM framework to ensure that the device's runtime
PM state matches the regulators state:
1. at the end of probe() function: set runtime PM state to active, so
there will be no spurious call to resume();
2. in remove(), ensure that resume() is called before disabling runtime PM
management and unconditionally disabling the regulators.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>