Documentation: mic: fix kernel version

v3.20 doesn't exist. heartbeat_enable was actually added in v4.4.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-class-mic.txt

@@ -153,7 +153,7 @@ Description:
 
 What:		/sys/class/mic/mic(x)/heartbeat_enable
 Date:		March 2015
-KernelVersion:	3.20
+KernelVersion:	4.4
 Contact:	Ashutosh Dixit <ashutosh.dixit@intel.com>
 Description:
 		The MIC drivers detect and inform user space about card crashes