soc: qcom: mdt_loader: Extract PAS operations

Rather than passing a boolean to indicate if the PAS operations should
be performed from within __mdt_load(), extract them to their own helper
function.

This will allow clients to invoke this directly, with some
qcom_scm_pas_metadata context that they later needs to release, without
further having to complicate the prototype of qcom_mdt_load().

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