perf symbols: Properly align symbol_conf.priv_size

If symbol_conf.priv_size is not a multiple of "sizeof(u64)" we'll bus
error on sparc64 in symbol__new because the "struct symbol *" pointer
is computed by adding symbol_conf.priv_size to the memory allocated.

We cannot isolate the fix to symbol__new and symbol__delete since the
private area is computed by subtracting the priv_size value from a
"struct symbol" pointer, so then the private area can still be
potentially unaligned.

So, simply align the symbol_conf.priv_size value in symbol__init()

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110328.175849.112593455.davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>