linuxPackages.perf: add libopcodes as a buildInput

Newer versions of perf in Linux 5.1+ support disassembling and
annotating eBPF programs inside the kernel. In order to do this, it uses
libbfd's support for bpf disassembly. There are two parts: libopcodes
and libbfd.

The 'perf' build system seems to expect libopcodes/libbfd to go "hand in
hand" -- always together, if one or the other is installed. If the build
system detects libbfd is available, then an import of <dis-asm.h> is
performed, but this fails since it wasn't in the buildInput. Fixing this
should be an easy, backwards-compatible change.

Fixes #60891, allowing linuxPackages_testing.perf to build again
(currently kernel version 5.1.0-rc7).

Signed-off-by: Austin Seipp <aseipp@pobox.com>