firmware: qcom: scm: Peripheral Authentication Service

This adds the Peripheral Authentication Service (PAS) interface to the
Qualcomm SCM interface. The API is used to authenticate and boot a range
of external processors in various Qualcomm platforms.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Andy Gross <andy.gross@linaro.org>