KVM: arm64: Convert the SVE guest vcpu flag to a vm flag

The vcpu flag GUEST_HAS_SVE is per-vcpu, but it is based on what
is now a per-vm feature. Make the flag per-vm.

Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20241216105057.579031-17-tabba@google.com


Signed-off-by: Marc Zyngier <maz@kernel.org>