dt-bindings: remoteproc: qcom: Add firmware bindings for Q6V5

Add optional "firmware-name" bindings for Q6V5 MSS and PAS based
remoteprocs. For Q6V5 MSS/PAS the two/one relative firmware
paths/path are to be listed respectively. Fallback to the default
images for mba/modem for Q6V5 MSS or the default Hexagon image
for Q6V5 PAS if the "firmware-name" binding is not present.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>