The HYP mode world switch in all its glory.

Implements save/restore of host/guest registers, EL2 trapping,
IPA resolution, and additional services (tlb invalidation).
Reviewed-by: NChristopher Covington <cov@codeaurora.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

This patch introduces several assembly macros and definitions used in
the .S files across arch/arm64/ like IRQ disabling/enabling, together
with asm-offsets.c.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NTony Lindgren <tony@atomide.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NNicolas Pitre <nico@linaro.org>
Acked-by: NOlof Johansson <olof@lixom.net>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>