target/arm: Implement AArch32 Hyp FARs

target/arm: Implement AArch32 Hyp FARs

The AArch32 virtualization extensions support these fault address
registers:
 * HDFAR: aliased with AArch64 FAR_EL2[31:0] and AArch32 DFAR(S)
 * HIFAR: aliased with AArch64 FAR_EL2[63:32] and AArch32 IFAR(S)

Implement the accessors for these. This fixes in passing a bug
where we weren't implementing the "RES0 from EL3 if EL2 not
implemented" behaviour for AArch64 FAR_EL2.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Luc Michel <luc.michel@greensocs.com>
Message-id: 20180814124254.5229-7-peter.maydell@linaro.org