ACPI / Battery: Add the check before refresh sysfs in the battery_notify()

In the commit 25be5821, add the refresh sysfs when system resumes
from suspending. But it didn't check that the battery exists. This
will cause battery sysfs files added when the battery doesn't exist.
This patch add the check before refreshing.

	https://bugzilla.kernel.org/show_bug.cgi?id=35642



Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>