perf bench mem: Rename 'routine' to 'function'

So right now there's a somewhat inconsistent mess of the benchmarking
code and options sometimes calling benchmarked functions 'functions',
sometimes calling them 'routines'.

Name them 'functions' consistently.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1445241870-24854-14-git-send-email-mingo@kernel.org


[ Updated perf-bench man page, pointed out by David Ahern ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>