score and mmix target_id

These targets currently use GENERIC_ELF_DATA as their target_id, but
that isn't exactly correct.  While their bfd tdata is generic elf,
their elf_section_data is extended with extra target data.  Add
MMIX_ELF_DATA and SCORE_ELF_DATA.

bfd/elf-bfd.h

@@ -556,6 +556,7 @@ enum elf_target_id
   METAG_ELF_DATA,
   MICROBLAZE_ELF_DATA,
   MIPS_ELF_DATA,
+  MMIX_ELF_DATA,
   MN10300_ELF_DATA,
   NDS32_ELF_DATA,
   OR1K_ELF_DATA,
@@ -563,6 +564,7 @@ enum elf_target_id
   PPC64_ELF_DATA,
   PRU_ELF_DATA,
   S390_ELF_DATA,
+  SCORE_ELF_DATA,
   SH_ELF_DATA,
   SPARC_ELF_DATA,
   SPU_ELF_DATA,

bfd/elf32-score.c

@@ -4447,6 +4447,7 @@ _bfd_score_elf_common_definition (Elf_Internal_Sym *sym)
 #define ELF_ARCH			bfd_arch_score
 #define ELF_MACHINE_CODE		EM_SCORE
 #define ELF_MACHINE_ALT1		EM_SCORE_OLD
+#define ELF_TARGET_ID			SCORE_ELF_DATA
 #define ELF_MAXPAGESIZE			0x8000
 
 #define elf_info_to_howto		NULL

bfd/elf64-mmix.c

@@ -2861,6 +2861,7 @@ mmix_elf_relax_section (bfd *abfd,
 
 #define ELF_ARCH		bfd_arch_mmix
 #define ELF_MACHINE_CODE	EM_MMIX
+#define ELF_TARGET_ID		MMIX_ELF_DATA
 
 /* According to mmix-doc page 36 (paragraph 45), this should be (1LL << 48LL).
    However, that's too much for something somewhere in the linker part of