power: reset: msm: Deassert PS_HOLD via SCM if possible

Support a new SCM call which disables the PMIC arbiter and
deasserts PS_HOLD in a single operation. Fall back on the
legacy behavior of disabling the PMIC abriter and directly
deasserting PS_HOLD if this call is not available.

This is necessary comply with atomicity requirements of the
secure environment.

Change-Id: Ia3b13d469932edf94d3249fa3e7234a1c12eee1b
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>