Fix ELF support for big endian SH

Fix ELF support for big endian SH

Fix the following build failure with big endian SH (e.g. sh4aeb):

  ,---
  In file included from nlist.c:44:
  nlist.c: In function '__elf_is_okay__':
  local-elf.h:223:25: error: 'ELFDATA2LMSB' undeclared (first use in this function); did you mean 'ELFDATA2LSB'?
    223 | #define ELF_TARG_DATA   ELFDATA2LMSB
        |                         ^~~~~~~~~~~~
  `---

Fixes: http://autobuild.buildroot.org/results/2980fb79c208454195d77383f1ece9afbd7f981b
Closes: !19
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Guillem Jover <guillem@hadrons.org>