oprofile: Don't set HAVE_LIBBFD when not using the prebuilt toolchain

The oprofile Makefiles complain about not finding exported libbfd
includes when using a different toolchain.

Change-Id: I029d3e39f1ccfdf193e1186e631992b69f9751e5
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>