fix: add wget package to docker dependencies

In order to support [1], add the wget package dependency to Hafnium
docker file.

[1] https://ci.trustedfirmware.org/job/hafnium-spmc-test-fvp/

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I4cf768b1ca2906ee237da6fa2f438e598e9d458b
diff --git a/bionic-amd64-hafnium/Dockerfile b/bionic-amd64-hafnium/Dockerfile
index 23573c9..33e90de 100644
--- a/bionic-amd64-hafnium/Dockerfile
+++ b/bionic-amd64-hafnium/Dockerfile
@@ -24,6 +24,7 @@
     python3-serial \
     strace \
     sudo \
+    wget \
 "
 
 # Can be overriden at build time