msm: msm_bus: Do not send tcs sets when size is 0

The RPMH driver is returning improper parameters when sending
TCS commands with array sizes 0. This occurs when the delta in a
client's vote is not large enough to cause a change in the threshold
values sent to hardware and causes no changes to the ACTIVE command
sets.

Change-Id: Iac017a26323fb2f453c9e3ef51951f5c106bd671
Signed-off-by: David Dai <daidavid1@codeaurora.org>