msm: ipa4: IPA PM remove callback requirement

Allow clients without callback to be registered to PM.
These clients are not expected to use any asynchronous
functions which requires a callback. In addition a sanity
check that if a callback is required from some reason,
an error will be printed to the log.

Change-Id: I407aa2dc6387263a567685797acb26999ac842d8
CRs-Fixed: 2120001
Signed-off-by: Michael Adisumarta <madisuma@codeaurora.org>