regulator: max8998: Remove wrong set_suspend_[en|dis]able callback settings

Using the same ops for both [en|dis]able and set_suspend_[en|dis]able
callbacks is actively broken. This patch removes .set_suspend_disable and
.set_suspend_enable callback setting.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>