ARM: migrate to common PSCI client code

Now that the common PSCI client code has been factored out to
drivers/firmware, and made safe for 32-bit use, move the 32-bit ARM code
over to it. This results in a moderate reduction of duplicated lines,
and will prevent further duplication as the PSCI client code is updated
for PSCI 1.0 and beyond.

The two legacy platform users of the PSCI invocation code are updated to
account for interface changes. In both cases the power state parameter
(which is constant) is now generated using macros, so that the
pack/unpack logic can be killed in preparation for PSCI 1.0 power state
changes.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>