KVM: arm64: Use kvzalloc() for kvm struct allocation

KVM: arm64: Use kvzalloc() for kvm struct allocation

Physically-allocated KVM structs aren't necessary when in VHE mode as
there's no need to share with the hyp's address space. Of course, there
can still be a performance benefit from physical allocations.

Use kvzalloc() for opportunistic physical allocations.

Acked-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://msgid.link/20251119093822.2513142-3-oupton@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>