perf tools: Fix fallback to cplus_demangle() when bfd_demangle() is not available

perf tools: Fix fallback to cplus_demangle() when bfd_demangle() is not available

make version 3.80 doesn't support "else ifdef" on the same line, also it
doesn't support unindented nested constructs.

Build fails with:
Makefile:608: Extraneous text after `else' directive
Makefile:611: *** only one `else' per conditional.  Stop.

This patch fixes the build for make 3.80.

Cc: Ingo Molnar <mingo@elte.hu>,
Cc: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <1278430783-17259-1-git-send-email-conny.seidel@amd.com>
Signed-off-by: Conny Seidel <conny.seidel@amd.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>