target/arm: Prepare DBGBVR and DBGWVR for FEAT_LVA

target/arm: Prepare DBGBVR and DBGWVR for FEAT_LVA

The original A.a revision of the AArch64 ARM required that we
force-extend the addresses in these registers from 49 bits.
This language has been loosened via a combination of IMPLEMENTATION
DEFINED and CONSTRAINTED UNPREDICTABLE to allow consideration of
the entire aligned address.

This means that we do not have to consider whether or not FEAT_LVA
is enabled, and decide from which bit an address might need to be
extended.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220301215958.157011-9-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>