msm: msm_bus: Disallow 0 bw requests during early init

Any clients attempting to request 0 bandwidth during init time
is not immediately honored and flushed out at late init. This is
to prevent clients from turning off vital shared resources that
other clients may need but have not had a chance to probe and vote
yet.

Change-Id: I2e237a1d537720ad8e53c2cf38ab024273186a30
Signed-off-by: David Dai <daidavid1@codeaurora.org>