edk2-hikey960: update ATF git repository location
edk2-hikey960: update ATF git repository location

HiKey960 is now merged into the integration branch of the official ATF
repository:
https://github.com/ARM-software/arm-trusted-firmware/tree/integration

Signed-off-by: Fathi Boudra <7cd6e55cc07a66bc71d7901a4cddfe6c22aab659@linaro.org>

kraj/meta-96boards,fboudra/meta-96boards,mrchapp/meta-96boards,kraj/meta-96boards,96boards/meta-96boards