target/arm: Promote consecutive memory ops for aa64

target/arm: Promote consecutive memory ops for aa64

For a sequence of loads or stores from a single register,
little-endian operations can be promoted to an 8-byte op.
This can reduce the number of operations by a factor of 8.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181011205206.3552-5-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>