misc: Add Arm contributions to gem5-20 RELEASE-NOTES.md

* Arm architectural extensions
* Arm TFA support
* DRAM changes

Change-Id: I434c501ee8413c8cd64af25c2c18eabf45e3ee77
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Wendy Elsasser <wendy.elsasser@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28908
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: 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 6f80906..0e52e5d 100644
--- a/RELEASE-NOTES.md
+++ b/RELEASE-NOTES.md
@@ -9,3 +9,11 @@
 * 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.
+* Implemented ARMv8.3-CompNum, SIMD complex number extension.
+* Support for Arm Trusted Firmware + u-boot with the new VExpress_GEM5_Foundation platform.
+* Changes in the DRAM Controller:
+    1) Added support for verifying available command bandwidth.
+    2) Added support for multi-cycle commands.
+    3) Added new timing parameters.
+    4) Added ability to interleave bursts.
+    5) Added LPDDR5 configurations.