perf probe: Print an enum type variable in "enum variable-name" format when showing...

When showing accessible variables, an enum type variable was printed in
"variable-name" format. Change this format into "enum variable-name".

Signed-off-by: Hyeoncheol Lee <hyc.lee@gmail.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/1348713399-4541-1-git-send-email-hyc.lee@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>