To fully read the received rx data from FIFO both the command and data
has to be read. Currently we read command, data separately and process
them. By adding an offset parameter to RX FIFO peak accessor, command
and data can be read together, simplifying things.  So introduce this.
Acked-by: NArun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: NSricharan R <sricharan@codeaurora.org>
Signed-off-by: NBjorn Andersson <bjorn.andersson@linaro.org>