hrtimer: Handle failure of tick_init_highres() gracefully

Commit 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
drops the return code of hrtimer_switch_to_hres(). While doing so, it also
drops the return statement itself on failure. This may cause a system hang.
Seen when running arm:multi_v7_defconfig in qemu with devicetree file
vexpress-v2p-ca9.

Fixes: 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Link: http://lkml.kernel.org/r/1440231047-16256-1-git-send-email-linux@roeck-us.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/time/hrtimer.c

@@ -695,6 +695,7 @@ static void hrtimer_switch_to_hres(void)
 	if (tick_init_highres()) {
 		printk(KERN_WARNING "Could not switch to high resolution "
 				    "mode on CPU %d\n", base->cpu);
+		return;
 	}
 	base->hres_active = 1;
 	hrtimer_resolution = HIGH_RES_NSEC;