ACPI: ec: add unlock in error path

Signed-off-by: Alexey Starikovskiy <alexey.y.starikovskiy@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 743ce27..8f5aaf7 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -280,8 +280,10 @@
 	mutex_lock(&ec->lock);
 	if (ec->global_lock) {
 		status = acpi_acquire_global_lock(ACPI_EC_UDELAY_GLK, &glk);
-		if (ACPI_FAILURE(status))
+		if (ACPI_FAILURE(status)) {
+			mutex_unlock(&ec->lock);
 			return -ENODEV;
+		}
 	}
 
 	/* Make sure GPE is enabled before doing transaction */