msm: cpp: Ensure CPP RX fifo is empty before writing payload

CPP RX FIFO empty status is not checked for payload start code and
trailer. A continuous counter must be used across the payload
instead of separate check for CPP RX FIFO empty status for
stripe and plane based. Ensure that CPP RX FIFO empty before
writing the second payload.

Change-Id: I11d0f77798addf4d654122e346dc6ec736a47113
Signed-off-by: Krishnankutty Kolathappilly <kkolatha@codeaurora.org>