arm-trusted-firmware: add EL2 boot patch from meta-agl-bsp

To generate a-t-f binaries equivalent to what is built for the other
H3 based boards in the AGL build process, add the KVM enabling patch
that is added by meta-agl-bsp.  It is still unclear if there is a
straightforward path to working the separate a-t-f build for the
reference hardware into the AGL h3ulcb build, so this duplication
seems like a necessary evil for now.

Bug-AGL: SPEC-3658

Signed-off-by: Scott Murray <scott.murray@konsulko.com>