jammy-amd64-tf-a-build: update rustup target

From aarch64-unknown-none to aarch64-unknown-none-softfloat.

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I7799afa05344ea2e4389f3e407bc5a6d039a025f
diff --git a/jammy-amd64-tf-a-build/Dockerfile b/jammy-amd64-tf-a-build/Dockerfile
index c02eb61..da1ff34 100644
--- a/jammy-amd64-tf-a-build/Dockerfile
+++ b/jammy-amd64-tf-a-build/Dockerfile
@@ -113,7 +113,7 @@
 RUN set -ex ;\
     cargo install 'tokei@12.1.*' ;\
     cargo install cargo-binutils ;\
-    rustup target add aarch64-unknown-none ;\
+    rustup target add aarch64-unknown-none-softfloat ;\
     rustup component add llvm-tools rustfmt
 
 ENV NVM_DIR="/home/buildslave/.nvm"