powerpc/xmon: Enable disassembly files (compilation changes)

After updating ppc-dis.c, ppc-opc.c and ppc.h the following changes were
made to enable compilation and working of xmon:

  1.  Remove all disassembler_info
  2.  Use xmon's printf/print_address to output data and addresses
      respectively.
  3.  All bfd_* types and casts have been removed.
  4.  Optimizations related to opcd_indices have been removed.
  5.  The dialect is set based on cpu features.
  6.  PPC_OPCODE_CLASSIC is no longer supported in the new
      disassembler.
  7.  VLE opcode parsing and printing has been stripped.
  8.  Coding style conventions used for those routines has
      been retained and it does not match our CodingStyle.
  9.  The highest supported dialect is POWER9.
  10. Defined ATTRIBUTE_UNUSED in ppc-dis.c.
  11. Defined _(x) in ppc-dis.c.

Finally, we remove the dependency on BROKEN so that XMON_DISASSEMBLY can
be enabled again.

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>