target/arm/ptw: Set attributes correctly for MMU disabled data accesses

target/arm/ptw: Set attributes correctly for MMU disabled data accesses

When the MMU is disabled, data accesses should be Device nGnRnE,
Outer Shareable, Untagged.  We handle the other cases from
AArch64.S1DisabledOutput() correctly but missed this one.
Device nGnRnE is memattr == 0, so the only part we were missing
was that shareability should be set to 2 for both insn fetches
and data accesses.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230807141514.19075-13-peter.maydell@linaro.org