target/arm: Add MTE bits to tb_flags

target/arm: Add MTE bits to tb_flags

Cache the composite ATA setting.

Cache when MTE is fully enabled, i.e. access to tags are enabled
and tag checks affect the PE.  Do this for both the normal context
and the UNPRIV context.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200626033144.790098-9-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>