Revert "UPSTREAM: PM / wakeup updates"

This is a preparation change for merging android-4.19.95 into
msm-4.19 branch.

The following changes are reverted. They will be reintroduced to
msm-4.19 at later stage.

2d67117d UPSTREAM: PM / wakeup: Drop wakeup_source_drop()
8f35ee2a UPSTREAM: PM / wakeup: Drop wakeup_source_init(), wakeup_source_prepare()
5bc2bdfb UPSTREAM: PM / wakeup: Use wakeup_source_register() in wakelock.c
2c9f5fa9 UPSTREAM: PM / wakeup: Show wakeup sources stats in sysfs
b5e87d65 UPSTREAM: PM / wakeup: Fix sysfs registration error path
845f6437 UPSTREAM: PM / wakeup: Register wakeup class kobj after device is added
47b82948 UPSTREAM: PM / wakeup: Unexport wakeup_source_sysfs_{add,remove}()

Change-Id: Ie43df2e4d512d4641030dcd7b4c608fb51da802a
Signed-off-by: Ivaylo Georgiev <irgeorgiev@codeaurora.org>