lts: new downloads area for LTS v2.8

Adding new shell script to use new
"https://downloads.trustedfirmware.org/tf-a-lts-v2.8"
downloads area for LTS v2.8 branch.

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: I972568832205f3d0580fac61d305d415d2fb3bf4
2 files changed