ext: Fix SST Documentation links

This documentation links to v21-2 resources. This is incorrect, they
should point towards v22-0 resources. This patch fixes this.

Change-Id: I0e4868327e0b216619e524c2329f57bbe40d3eae
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61712
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
diff --git a/ext/sst/README.md b/ext/sst/README.md
index dbec200..d9bbe85 100644
--- a/ext/sst/README.md
+++ b/ext/sst/README.md
@@ -62,7 +62,7 @@
 Downloading the built bootloader containing a Linux Kernel and a workload,
 
 ```sh
-wget http://dist.gem5.org/dist/v21-2/misc/riscv/bbl-busybox-boot-exit
+wget http://dist.gem5.org/dist/v22-0/misc/riscv/bbl-busybox-boot-exit
 ```
 
 Running the simulation
@@ -87,7 +87,7 @@
 directory):
 
 ```sh
-wget http://dist.gem5.org/dist/v21-2/arm/aarch-sst-20211207.tar.bz2
+wget http://dist.gem5.org/dist/v22-0/arm/aarch-sst-20211207.tar.bz2
 tar -xf aarch-sst-20211207.tar.bz2
 
 # copying bootloaders