ACPI: EC: Use fast path in acpi_ec_add() for DSDT boot EC

If the boot EC comes from the DSDT, its ACPI handle is equal to the
handle of a device object with the PNP0C09 device ID.  If that
device object is passed to acpi_ec_add(), it is not necessary to
allocate a new EC structure for it and parse it, because that has
been done already, so change the function to use the fast path in
that case.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/ec.c

@@ -1611,7 +1611,8 @@ static int acpi_ec_add(struct acpi_device *device)
 	strcpy(acpi_device_name(device), ACPI_EC_DEVICE_NAME);
 	strcpy(acpi_device_class(device), ACPI_EC_CLASS);
 
-	if (!strcmp(acpi_device_hid(device), ACPI_ECDT_HID)) {
+	if ((boot_ec && boot_ec->handle == device->handle) ||
+	    !strcmp(acpi_device_hid(device), ACPI_ECDT_HID)) {
 		/* Fast path: this device corresponds to the boot EC. */
 		ec = boot_ec;
 	} else {