faq: Mention Linux kernel versions supported by 2.13.x.
This is based on acinclude.m4 in branch-2.13, which rejects anything
newer than 5.0.
Reported-by: Han Zhou
Acked-by: Greg Rose
Acked-by: Flavio Leitner
@@ -70,6 +70,7 @@ Q: What Linux kernel versions does each Open vSwitch release work with?
2.10.x 3.16 to 4.17
2.11.x 3.16 to 4.18
2.12.x 3.16 to 5.0
+ 2.13.x 3.16 to 5.0
2.14.x 3.16 to 5.5
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