MIPS: Don't place cu2 notifiers in __cpuinitdata

The notifiers may be called at any time, so the notifier_block cannot
be in init memory.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1592/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>