perf annotate: Generalize handling of 'ret' instructions

Introduce helper to detect 'ret' instructions and use the same in the TUI.
A helper is needed since some architectures such as powerpc have more
than one return instruction.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: http://lkml.kernel.org/r/1466769240-12376-5-git-send-email-ravi.bangoria@linux.vnet.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>