perf symbols: Avoid unnecessary symbol loading when dso list is specified

We were performing the full thread__find_addr_location
operation, i.e. resolving to a map/dso _and_ loading its symbols
when we can optimize it by first calling thread__find_addr_map
to find just the map/dso, check if it is one that we are
interested in (passed via --dsos/-d in 'perf annotate', 'perf
report', etc) and if not avoid loading the symtab.

Nice speedup when we know which DSO we're interested in.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1269459619-982-2-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>