tracing: have function trace select kallsyms

Impact: fix output of function tracer to be useful

The function tracer is pretty useless if KALLSYMS is not configured.
Unless you are good at reading hex values, the function tracer should
select the KALLSYMS configuration.

Also, the dynamic function tracer will fail its self test if KALLSYMS
is not selected.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>