arm64: Fix compat register mappings

For reasons not entirely apparent, but now enshrined in history, the
architectural mapping of AArch32 banked registers to AArch64 registers
actually orders SP_<mode> and LR_<mode> backwards compared to the
intuitive r13/r14 order, for all modes except FIQ.

Fix the compat_<reg>_<mode> macros accordingly, in the hope of avoiding
subtle bugs with KVM and AArch32 guests.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>