soc: qcom: watchdog_v2: Add support for the new scm_call2 API

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: Id5a75936f6c1881add09b3dc9b07abecbda694eb
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>