perf annotate: Cleanup disasm__calc_percent()

perf annotate: Cleanup disasm__calc_percent()

The loop end condition is calculated from next disasm_line or the symbol
size if it's the last disasm_line.  But it doesn't need to be calculated
at every iteration.  Moving it out of the function can simplify code a
bit.  Also the src_line doesn't need to be checked in every time.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1362462812-30885-5-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>