UPSTREAM: PM / wakeup: Use wakeup_source_register() in wakelock.c

kernel/power/wakelock.c duplicates wakeup source creation and
registration code from drivers/base/power/wakeup.c.

Change struct wakelock's wakeup source to a pointer and use
wakeup_source_register() function to create and register said wakeup
source. Use wakeup_source_unregister() on cleanup path.

Signed-off-by: Tri Vo <trong@android.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 2434aea58e652a9fe114181ac90aa60e2f2e1b25)
Bug: 129087298
Signed-off-by: Tri Vo <trong@google.com>
Change-Id: I4e6b3c613c561fb382f17c3c31b6584aebabfb5d