powerpc: perf_event: Cleanup output by adding symbols

Add some dummy symbols for the branches at 0xf00, 0xf20 and 0xf40,
otherwise hits end up in trap_0e which is confusing to the user.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>