The general purpose registers in AArch32 are mapped in an
architecturally defined manner into the AArch64 registers.

It allows the AArch32 registers of an application or a virtual
machine to be inspected by the OS or an hypervisor.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>