FROMLIST: firmware/smccc: Call arch-specific hook on discovering KVM services

arm64 will soon require its own callback to initialise services
that are only availably on this architecture. Introduce a hook
that can be overloaded by the architecture.

Link: https://lore.kernel.org/r/20211004174849.2831548-12-maz@kernel.org


Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Bug: 233587962
Change-Id: I743e1786df1477b3c9fab0fe2e5ea52a7dcdf01f
Signed-off-by: Will Deacon <willdeacon@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>