perf tools: Remove unneeded magic.h include from util.h

perf tools: Remove unneeded magic.h include from util.h

Not used anymore, IIRC it was for useless PROC_FS_MAGIC procfs checks,
but those are long gone.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-v027did3kvj0vz7bofgzkw29@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>