perf kmem: Fixup the symbol address before using it

We get absolute addresses in the events, but relative ones from the
symbol subsystem, so calculate the absolute address by asking for the
map where the symbol was found, that has the place where the DSO was
actually loaded.

For the core kernel this poses no problems if the kernel is not
relocated by things like kexec, or if we use /proc/kallsyms, but for
modules we were getting really large, negative offsets.

LKML-Reference: <new-submission>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>