PM / devfreq: Use the new scm_call2 API in the MSM Adreno governor

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

Change-Id: Ice63cdbdaca3ed8c825cd224c86941a796a9a2d6
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>