perf: Use read() instead of lseek() in trace_event_read.c:skip()

This is a small fix for a problem affecting live-mode, introduced
recently:

root@tropicana:~# perf trace rwtop
perf trace started with Perl
script /root/libexec/perf-core/scripts/perl/rwtop.pl

  Fatal: did not read header event

commit d00a47cc added a skip()
function to skip over e.g. header_page, but this doesn't work for
live mode.  This patch re-implements skip() to use read() instead of
lseek() to fix that.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1273032130.6383.28.camel@tropicana>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>