serial: msm_geni_serial: Remove power vote when cancelling Tx sequencer

If the Tx sequencer was running during the stop_tx() function call then it
means that there is an extra power vote that should be removed.
A start_tx() always puts in a power vote that is removed as part of the
ISR that reports a transmit done. If a Tx is stuck due to flow control then
the transmit done ISR won't come, so when there is a call to stop_tx()
from the client code, then remove this extra vote.
Modify some of the IPC logging messages.

Change-Id: Ic844eb72b295107942db1005e168e568f938e6d8
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>