llvm-readobj: Try the DWARF CFI dumper on all machines.

There's no reason to limit the DWARF CFI dumper to EM_386 and EM_X86_64;
ELF files could contain DWARF CFI on almost any platform (even 32-bit ARM;
NetBSD uses DWARF CFI on that platform). So start using the DWARF CFI dumper
unconditionally so that we can dump .eh_frame sections on the remaining ELF
platforms as well as in NetBSD binaries.

Differential Revision: https://reviews.llvm.org/D58761

llvm-svn: 355151