target/rx: Use little-endian variant of cpu_ld/st_data*()

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

Mechanical change running:

  $ tgt=rx; \
    end=le; \
    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: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Message-ID: <20251126202200.23100-5-philmd@linaro.org>