In system mode, abi_ptr is primarily used for representing addresses
when accessing guest memory with cpu_[st|ld]*(). Widening it from
target_ulong to vaddr reduces the target dependence of these functions
and is step towards building accel/ once for system mode.

Signed-off-by: Anton Johansson <anjo@rev.ng>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230807155706.9580-7-anjo@rev.ng>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>