rcu: Add rcutorture CPU-hotplug capability" adds cpu hotplug operations
to the rcutorture code but produces a false positive warning about section
mismatches:

WARNING: vmlinux.o(.text+0x1e420c): Section mismatch in reference from the
function rcu_torture_onoff() to the function .cpuinit.text:cpu_up()
The function rcu_torture_onoff() references
the function __cpuinit cpu_up().
This is often because rcu_torture_onoff lacks a __cpuinit
annotation or the annotation of cpu_up is wrong.

Just add a __cpuinit annotation so the warning goes away.

Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>