Commit dc99065b (v0.1.0) added dis-asm.h from binutils.

Commit 43d4145a (v0.1.5) inlined bfd.h into dis-asm.h to remove the
dependency on binutils.

Commit 76cad711 (v1.4.0) moved dis-asm.h to include/disas/bfd.h.
The new name is confusing when you try to match against (pre GPLv3+)
binutils.  Rename it back.  Keep it in the same directory, of course.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190417191805.28198-17-armbru@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Coverity warnings CID 1385146, 1385148 1385149 and 1385150 point that
xtensa_opcode_num_operands and xtensa_format_num_slots may return -1
even when xtensa_opcode_decode and xtensa_format_decode succeed. In that
case unsigned counters used to iterate through operands/slots will not
do the right thing.
Make counters and loop bounds signed to fix the warnings.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Add disas/xtensa.c and use libisa for instruction decoding/opcode name
lookup.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>