target-arm: Correct sense of the DCZID DZP bit

target-arm: Correct sense of the DCZID DZP bit

The DZP bit in the DCZID system register should be set if
the control bits which prohibit use of the DC ZVA instruction
have been set (it stands for Data Zero Prohibited). However
we had the sense of the test inverted; fix this so that the
bit reads correctly.

To avoid this regressing the behaviour of the user-mode
emulator, we must set the DZE bit in the SCTLR for that
config so that userspace continues to see DZP as zero (it
was getting the correct result by accident previously).

Reported-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Christopher Covington <cov@codeaurora.org>
Message-id: 1412959792-20708-1-git-send-email-peter.maydell@linaro.org