remoteproc: qcom: mdt_loader: Make the firmware authentication optional

qcom_mdt_load function loads the mdt type firmware and
initialises the secure memory as well. Make the initialisation only
when requested by the caller, so that the function can be used
by self-authenticating remoteproc as well.

Acked-by: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>