UPSTREAM: ARM: 8478/2: arm/arm64: add arm-smccc

UPSTREAM: ARM: 8478/2: arm/arm64: add arm-smccc

Adds helpers to do SMC and HVC based on ARM SMC Calling Convention.
CONFIG_HAVE_ARM_SMCCC is enabled for architectures that may support the
SMC or HVC instruction. It's the responsibility of the caller to know if
the SMC instruction is supported by the platform.

This patch doesn't provide an implementation of the declared functions.
Later patches will bring in implementations and set
CONFIG_HAVE_ARM_SMCCC for ARM and ARM64 respectively.

Change-Id: I7b403bb56c05a52e248cb02f154e2ab31c62fddf
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
(cherry picked from commit 98dd64f34f47ce19b388d9015f767f48393a81eb)