target-arm/translate.c: Use get_mem_index() for SRS memory accesses

target-arm/translate.c: Use get_mem_index() for SRS memory accesses

The SRS instruction was using a hardcoded 0 for the memory
accesses. This happens to be OK since the SRS instruction is
UNPREDICTABLE in User and System modes, but is awkward if we
want to rearrange the MMU index uses. Switch to using
get_mem_index() like all the other accesses.

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1400980132-25949-4-git-send-email-edgar.iglesias@gmail.com