configs/targets: Forbid s390x to use legacy native endianness APIs

All s390x-related binaries are buildable without a single
use of the legacy "native endian" API. Set the transitional
TARGET_NOT_USING_LEGACY_NATIVE_ENDIAN_API definition to forbid
further uses of the legacy API.

Preliminary commits allowing this final change:

 . f0853c2586 target/s390x: Inline translator_lduw() and translator_ldl()
 . ee4dae6a33 target/s390x: Use big-endian variant of cpu_ld/st_data*()
 . 381a1fda5b target/s390x: Inline cpu_ld{uw, l}_code() calls in EX opcode helper
 . 69da23130f target/s390x: Replace MO_TE -> MO_BE
 . 0fb6ad781c target/s390x: Replace gdb_get_regl() -> gdb_get_reg64()
 . 409cbb1a61 target/s390x: Use explicit big-endian LD/ST API
 . 6d9dad7126 target/s390x: Replace HOST_BIG_ENDIAN #ifdef with if() check

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20251224162036.90404-9-philmd@linaro.org>

configs/targets/s390x-linux-user.mak

@@ -4,3 +4,4 @@ TARGET_SYSTBL=syscall.tbl
 TARGET_BIG_ENDIAN=y
 TARGET_XML_FILES= gdb-xml/s390x-core64.xml gdb-xml/s390-acr.xml gdb-xml/s390-fpr.xml gdb-xml/s390-vx.xml gdb-xml/s390-cr.xml gdb-xml/s390-virt.xml gdb-xml/s390-virt-kvm.xml gdb-xml/s390-gs.xml
 TARGET_LONG_BITS=64
+TARGET_NOT_USING_LEGACY_NATIVE_ENDIAN_API=y

configs/targets/s390x-softmmu.mak

@@ -3,3 +3,4 @@ TARGET_BIG_ENDIAN=y
 TARGET_KVM_HAVE_GUEST_DEBUG=y
 TARGET_XML_FILES= gdb-xml/s390x-core64.xml gdb-xml/s390-acr.xml gdb-xml/s390-fpr.xml gdb-xml/s390-vx.xml gdb-xml/s390-cr.xml gdb-xml/s390-virt.xml gdb-xml/s390-virt-kvm.xml gdb-xml/s390-gs.xml
 TARGET_LONG_BITS=64
+TARGET_NOT_USING_LEGACY_NATIVE_ENDIAN_API=y