feat(coverity): add SPMC_AT_EL3=1 build for hikey960

Make sure that SPMC_AT_EL3 continues to work on hikey960 platform.
This was triggered by the patch series here:
[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/16283/3

Signed-off-by: Lukas Hanel <lukas.hanel@trustonic.com>
Change-Id: I2088a1d0df2a4bb7a03f9d5f443d21c93af142de
1 file changed