msm: pm-8x60: Move hotplug related code out of pm code.
Move hotplug related code into otplug.c and compile hotplug.c only when
CONFIG_HOTPLUG_CPU is defined.

Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
Change-Id: Ia9aa7a64e9831f52431c77c22f30fb64892efaea