perf symbols: Accept an alias when looking for "_text"

As it is in PARISC64:

parisc:~# uname -a
Linux parisc 2.6.33-rc4-tip+ #1 SMP Thu Jan 14 13:33:34 BRST
2010 parisc64 GNU/Linux parisc:~# grep -w _text /proc/kallsyms
0000000040100000 A _text
parisc:~# grep 0000000040100000 /proc/kallsyms
0000000040100000 T stext
0000000040100000 T _stext
0000000040100000 A _text
parisc:~#

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: <1263586107-1756-2-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>