docs: ABI: sysfs-class-net: fix a typo

clas->class
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/4bba2a1592df5a9435c8d4757a9abf20246e2a99.1604312590.git.mchehab+huawei@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-class-net

@@ -152,7 +152,7 @@ Description:
 		When an interface is under test, it cannot be expected
 		to pass packets as normal.
 
-What:		/sys/clas/net/<iface>/duplex
+What:		/sys/class/net/<iface>/duplex
 Date:		October 2009
 KernelVersion:	2.6.33
 Contact:	netdev@vger.kernel.org