RELNOTES: mention inline IPSEC offload

Reviewed by:	emaste
Sponsored by:	NVidia networking
Differential revision:	https://reviews.freebsd.org/D51779

RELNOTES

@@ -10,6 +10,10 @@ newline.  Entries should be separated by a newline.
 
 Changes to this file should not be MFCed.
 
+ef2a572bf6:
+	Inline IPSEC offload infrastructure and driver support for mlx5(4)
+	Nvidia ConnectX-6+ network cards were added.
+
 68ba38dad3:
 	amd64: handling of the %fsbase/%gsbase registers and tls base
 	were reworked, making it more useful for apps that directly