linux-user/microblaze: Fix little-endianness binary

MicroBlaze CPU model has a "little-endian" property, pointing to
the @endi internal field. Commit c36ec3a965 ("hw/microblaze:
Explicit CPU endianness") took care of having all MicroBlaze
boards with an explicit default endianness, so later commit
415aae543e ("target/microblaze: Consider endianness while
translating code") could infer the endianness at runtime from
the @endi field, and not a compile time via the TARGET_BIG_ENDIAN
definition. Doing so, we forgot to make the endianness explicit
on user emulation, so there all CPUs are started with the default
"little-endian=off" value, leading to breaking support for little
endian binaries:

  $ readelf -h ./hello-world-mbel
  ELF Header:
    Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
    Class:                             ELF32
    Data:                              2's complement, little endian

  $ qemu-microblazeel ./hello-world-mbel
  qemu: uncaught target signal 11 (Segmentation fault) - core dumped
  Segmentation fault (core dumped)

Fix by restoring the previous behavior of starting with the
builtin endianness of the binary:

  $ qemu-microblazeel ./hello-world-mbel
  Hello World

Cc: qemu-stable@nongnu.org
Fixes: 415aae543e ("target/microblaze: Consider endianness while translating code")
Reported-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Message-Id: <20251006173350.17455-1-philmd@linaro.org>

linux-user/microblaze/elfload.c

@@ -8,7 +8,8 @@
 
 const char *get_elf_cpu_model(uint32_t eflags)
 {
-    return "any";
+    return TARGET_BIG_ENDIAN ? "any,little-endian=off"
+                             : "any,little-endian=on";
 }
 
 void elf_core_copy_regs(target_elf_gregset_t *r, const CPUMBState *env)