msm: vidc: Fix setting layer bitrate

Layer bitrates should be enabled only when hierp layer is set.
Add a check to return when max hierp layer or actual hierp layer
count is zero.

Change-Id: I38563c9f62447b760c0081ba095cda7140fca25f
Signed-off-by: Amit Shekhar <ashekhar@codeaurora.org>