MIPS: Move CPU Hotplug config option into submenu

The KConfig option HOTPLUG_CPU should appear in the "Kernel Type"
submenu. Relocate it to where SMP support is configured.

Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13751/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>