perf test: Fix vmlinux failure on s390x part 2

On s390x perf test 1 failed. It turned out that commit cf6383f7
("perf report: Fix kernel symbol adjustment for s390x") was incorrect.

The previous implementation in dso__load_sym() is also suitable for
s390x.

Therefore this patch undoes commit cf6383f7



Signed-off-by: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Cc: Zvonko Kosic <zvonko.kosic@de.ibm.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Fixes: cf6383f7

 ("perf report: Fix kernel symbol adjustment for s390x")
LPU-Reference: 20170915071404.58398-2-tmricht@linux.vnet.ibm.com
Link: http://lkml.kernel.org/n/tip-v101o8k25vuja2ogosgf15yy@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>