perf symbol: Move sym_entry->skip to symbol->ignore

While going thru each of the sym_entry fields looking to reduce it to
the set of entries needed when in an active symbols list, 'skip' should
really be in symbol, as we set it when loading the symtab.

And the space used by the basic symbol allocation remains the same as
we had 5 bytes of padding.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>