firmware: qcom_scm: Add support for Qualcomm Secure Execution Environment SCM interface

Add support for SCM calls to Secure OS and the Secure Execution
Environment (SEE) residing in the TrustZone (TZ) via the QSEECOM
interface. This allows communication with Secure/TZ applications, for
example 'uefisecapp' managing access to UEFI variables.

For better separation, make qcom_scm spin up a dedicated child
(platform) device in case QSEECOM support has been detected. The
corresponding driver for this device is then responsible for managing
any QSEECOM clients. Specifically, this driver attempts to automatically
detect known and supported applications, creating a client (auxiliary)
device for each one. The respective client/auxiliary driver is then
responsible for managing and communicating with the application.

While this patch introduces only a very basic interface without the more
advanced features (such as re-entrant and blocking SCM calls and
listeners/callbacks), this is enough to talk to the aforementioned
'uefisecapp'.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20230827211408.689076-3-luzmaximilian@gmail.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>