MAINTAINERS: Add include/linux/cpuhplock.h to CPU HOTPLUG area

The move of CPU hotplug function declarations to include/linux/cpuhplock.h
did not update the CPU HOTPLUG section of MAINTAINERS. Update it now.

Fixes: 195fb517ee25 ("cpu: Move CPU hotplug function declarations into their own header")
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/ef78e9d61d0ae041a1f44bd3cf8bb6e733b294d6.1780543665.git.reinette.chatre@intel.com