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 <[email protected]>
Reviewed-by: Edgar E. Iglesias <[email protected]>
Reviewed-by: Luc Michel <[email protected]>
Message-id: 20180814124254[email protected]