Add curl to docker image

Curl is an alternative for wget and used by some external tools.
So it's good to have both for flexibility.

Signed-off-by: Anton Bondarenko <anton.bondarenko@arm.com>

Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Approved-by: Viet-Hoa Do <viet-hoa.do@arm.com>