drivers: soc: qcom: Update scm-boot to use the new scm_call2 API

The secure world now sports an interface that is more
aligned to the ARMv8 SMC calling convention spec. Add
support for it by using the new scm_call2 API.

Change-Id: I696941c00b300a458ff62894cbfb3b57eb0db8d3
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>