misc: added news on RISC-V to RELEASE-NOTES.md.

Change-Id: I9b60cd2f533e6d4ce677e8a9b7bb5a5698e51c61
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28448
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
diff --git a/RELEASE-NOTES.md b/RELEASE-NOTES.md
index 1a679dd..6f80906 100644
--- a/RELEASE-NOTES.md
+++ b/RELEASE-NOTES.md
@@ -8,3 +8,4 @@
 * The m5 utility has been revamped with a new build system based on scons, tests, and updated and more consistent feature support.
 * Robust support for marshalling data from a function call inside the simulation to a function within gem5 using a predefined set of rules.
 * Workload configuration pulled out into its own object, simplifying the System object and making workload configuration more modular and flexible.
+* Sv39 paging has been added to the RISC-V ISA, bringing gem5 close to running Linux on RISC-V.