qcom: subsys-pil-tz: Add support for the new scm_call2 API

The scm library has added support for the new secure world
interface that is more aligned to the ARMv8 SMC calling
convention. Use the new API while maintaining backward
compatibility.

Change-Id: Ib2b5ed9ecae4a0c2bcc3caa818c701ec8774ab6f
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>