dev/psci: Create macros to simplify calling SMCCC

When calling into SMCCC functions we often only need a few arguments.
As the current function needs all 8 possible arguments to be set the
unused values will be zero.

Create a macro to pass in the used values, followed by enough zeros,
then the result pointer.

Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D46986