perf_counter tools: Adjust only prelinked symbol's addresses

I.e. we can't handle these two kinds of files in the same way:

1) prelinked system library:

[acme@doppio pahole]$ readelf -s /usr/lib64/libdw-0.141.so | egrep 'FUNC.+GLOBAL.+dwfl_report_elf'
   278: 00000030450105a0   261 FUNC    GLOBAL DEFAULT   12 dwfl_report_elf@@ELFUTILS_0.122

2) not prelinked library with debug information from a -debuginfo package:

[acme@doppio pahole]$ readelf -s /usr/lib/debug/usr/lib64/libdw-0.141.so.debug | egrep 'FUNC.+GLOBAL.+dwfl_report_elf'
   629: 00000000000105a0   261 FUNC    GLOBAL DEFAULT   12 dwfl_report_elf
[acme@doppio pahole]$

Now the numbers I got for a pahole perf run are in line with
the numbers I get from oprofile.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20090630144317.GB12663@ghostprotocols.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>