oprofile, s390: Fix section mismatch of function hws_cpu_callback()

Fixes the following section mismatch:

 Section mismatch in reference from the variable hws_cpu_notifier to the function .cpuinit.text:hws_cpu_callback()

Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>