PM: Fix unmet dependency warning from kconfig

Fix the following build warning:

warning: (PM_SLEEP_SMP && SMP && (ARCH_SUSPEND_POSSIBLE || \
ARCH_HIBERNATION_POSSIBLE) && PM_SLEEP) selects HOTPLUG_CPU which \
has unmet direct dependencies (SMP && HOTPLUG)

by selecting HOTPLUG along with CPU_HOTPLUG.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index cb57eb9..e45894c 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -86,6 +86,7 @@
 	depends on SMP
 	depends on ARCH_SUSPEND_POSSIBLE || ARCH_HIBERNATION_POSSIBLE
 	depends on PM_SLEEP
+	select HOTPLUG
 	select HOTPLUG_CPU
 	default y