target/s390x: Use big-endian variant of cpu_ld/st_data*()

We only build the S390x target using big endianness order,
therefore the cpu_ld/st_data*() definitions expand to the
big endian declarations. Use the explicit big-endian variants.

Mechanical change running:

  $ tgt=s390x; \
    end=be; \
    for op in data mmuidx_ra; do \
      for ac in uw sw l q; do \
        sed -i -e "s/cpu_ld${ac}_${op}/cpu_ld${ac}_${end}_${op}/" \
                  $(git grep -l cpu_ target/${tgt}/); \
      done;
      for ac in w l q; do \
        sed -i -e "s/cpu_st${ac}_${op}/cpu_st${ac}_${end}_${op}/" \
                  $(git grep -l cpu_ target/${tgt}/); \
      done;
    done

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20251224162036.90404-7-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>