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
1 file changed