mfd: wm8994-core: Disable regulators before removing them

The order in which resources were freed in wm8994_device_exit() isn't
correct. The regulators are removed before they are disabled.

Fix it by reordering code a bit, which makes it exact opposite of
wm8994_device_init() as well.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>