target-arm: Provide both 32 and 64 bit versions of debug registers

target-arm: Provide both 32 and 64 bit versions of debug registers

Bring the 32 bit and 64 bit views of the debug registers into
line by providing the same set of registers in both cases.
(This still isn't a complete set, but it is consistent.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>