KVM: arm64: nVHE: Pass host VA arguments as pointers

Four hypercalls take host VAs as unsigned long: the donated vm, pgd
and vcpu regions, and the tracing descriptor. Retype the arguments
and their EL2 consumers as void *, so that the typed hypercall
declarations introduced later in the series can attach a sparse
address space to them; an address space attaches only to pointers.

No functional change intended.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>