Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/Documentation/ABI/testing/sysfs-bus-thunderbolt b/Documentation/ABI/testing/sysfs-bus-thunderbolt
index 151584a..b21fba1 100644
--- a/Documentation/ABI/testing/sysfs-bus-thunderbolt
+++ b/Documentation/ABI/testing/sysfs-bus-thunderbolt
@@ -21,6 +21,15 @@
 		If a device is authorized automatically during boot its
 		boot attribute is set to 1.
 
+What: /sys/bus/thunderbolt/devices/.../domainX/iommu_dma_protection
+Date:		Mar 2019
+KernelVersion:	4.21
+Contact:	thunderbolt-software@lists.01.org
+Description:	This attribute tells whether the system uses IOMMU
+		for DMA protection. Value of 1 means IOMMU is used 0 means
+		it is not (DMA protection is solely based on Thunderbolt
+		security levels).
+
 What: /sys/bus/thunderbolt/devices/.../domainX/security
 Date:		Sep 2017
 KernelVersion:	4.13