arm, pm, vmpressure: add missing slab.h includes

arch/arm/mach-tegra/pm.c, kernel/power/console.c and mm/vmpressure.c
were somehow getting slab.h indirectly through cgroup.h which in turn
was getting it indirectly through xattr.h.  A scheduled cgroup change
drops xattr.h inclusion from cgroup.h and breaks compilation of these
three files.  Add explicit slab.h includes to the three files.

A pending cgroup patch depends on this change and it'd be great if
this can be routed through cgroup/for-3.14-fixes branch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: linux-tegra@vger.kernel.org
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-pm@vger.kernel.org
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: cgroups@vger.kernel.org

arch/arm/mach-tegra/pm.c

@@ -24,6 +24,7 @@
 #include <linux/cpu_pm.h>
 #include <linux/suspend.h>
 #include <linux/err.h>
+#include <linux/slab.h>
 #include <linux/clk/tegra.h>
 
 #include <asm/smp_plat.h>

kernel/power/console.c

@@ -9,6 +9,7 @@
 #include <linux/kbd_kern.h>
 #include <linux/vt.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 #include "power.h"
 
 #define SUSPEND_CONSOLE	(MAX_NR_CONSOLES-1)

mm/vmpressure.c

@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/vmstat.h>
 #include <linux/eventfd.h>
+#include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/printk.h>
 #include <linux/vmpressure.h>