binutils: generalize init_dwarf_regnames_by_* functions

binutils: generalize init_dwarf_regnames_by_* functions

This patch renames the functions:

  init_dwarf_regnames_by_elf_machine_code
  init_dwarf_regnames_by_bfd_arch_and_mach

to

  init_dwarf_by_elf_machine_code
  init_dwarf_by_bfd_arch_and_mach

The idea is to start using these functions to perform general
architecture/machine specific initializations beyond register names.

Regtested in x86_64-linux-gnu and aarch64-linux-gnu targets.

binutils/ChangeLog:

	* dwarf.c (init_dwarf_regnames_by_elf_machine_code): Rename to
	init_dwarf_by_elf_machine_code.
	(init_dwarf_regnames_by_bfd_arch_and_mach): Rename to
	init_dwarf_by_bfd_arch_and_mach.
	* dwarf.h: Adjust prototypes accordingly.
	* readelf.c (process_file_header): Adjust call to
	init_dwarf_regnames_by_elf_machine_code accordingly.
	* objdump.c (dump_dwarf): Adjust call to
	init_dwarf_regnames_by_bfd_arch_and_mach accordingly.