remoteproc: qcom: add more help text qcom options

With these more help text added, hopefully it's easier to understand the
distinctions of these qcom remoteproc drivers.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Link: https://lore.kernel.org/r/20201217030400.6235-1-shawn.guo@linaro.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>