target/s390x: Use cpu_*_mmuidx_ra instead of MMU_MODE*_SUFFIX

target/s390x: Use cpu_*_mmuidx_ra instead of MMU_MODE*_SUFFIX

The generated functions aside from *_real are unused.
The *_real functions have a couple of users in mem_helper.c;
use *_mmuidx_ra instead, with MMU_REAL_IDX.

Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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v2: Use *_mmuidx_ra directly, without intermediate macros.