char: hpet: fix a missing check of ioremap

Check if ioremap fails, and if so, return AE_ERROR.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/hpet.c

@@ -973,6 +973,8 @@ static acpi_status hpet_resources(struct acpi_resource *res, void *data)
 	if (ACPI_SUCCESS(status)) {
 		hdp->hd_phys_address = addr.address.minimum;
 		hdp->hd_address = ioremap(addr.address.minimum, addr.address.address_length);
+		if (!hdp->hd_address)
+			return AE_ERROR;
 
 		if (hpet_is_known(hdp)) {
 			iounmap(hdp->hd_address);