hw/intc/arm_gicv3_redist: Remove unnecessary zero checks

hw/intc/arm_gicv3_redist: Remove unnecessary zero checks

The ITS-related parts of the redistributor code make some checks for
whether registers like GICR_PROPBASER and GICR_PENDBASER are zero.
There is no requirement in the specification for treating zeroes in
these address registers specially -- they contain guest physical
addresses and it is entirely valid (if unusual) for the guest to
choose to put the tables they address at guest physical address zero.
We use these values only to calculate guest addresses, and attempts
by the guest to use a bad address will be handled by the
address_space_* functions which we use to do the loads and stores.

Remove the unnecessary checks.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220122182444.724087-9-peter.maydell@linaro.org