KVM: arm64: Bump the supported version of FF-A to 1.2

FF-A version 1.2 introduces the DIRECT_REQ2 ABI. Bump the FF-A version
preferred by the hypervisor to enable implementation of the 1.2-only
FFA_MSG_SEND_DIRECT_REQ2 and FFA_MSG_SEND_RESP2 messaging interfaces.

Co-developed-by: Ayrton Munoz <ayrton@google.com>
Signed-off-by: Ayrton Munoz <ayrton@google.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Per Larsen <perlarsen@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>