dsp: usf: update wakeup_source API

wakeup_source_init and wakeup_source_trash are removed in new kernel.
Update the two APIs to wakeup_source_register and wakeup_source_unregister.

Change-Id: I1e0b6e856dc2636032da68bf0e3d2be215d3ae8e
Signed-off-by: Dechen Chai <dchai@codeaurora.org>