arm64: kvm: Remove kern_hyp_va from get_vcpu_ptr

get_vcpu_ptr is an assembly accessor for the percpu value
kvm_host_data->host_ctxt.__hyp_running_vcpu. kern_hyp_va only applies to
nVHE however __hyp_running_vcpu is always assigned a pointer that has
already had kern_hyp_va applied in __kvm_vcpu_run_nvhe.

kern_hyp_va is currently idempotent as it just masks and inserts the
tag, but this could change in future and the second application is
unnecessary.

Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: James Morse <james.morse@arm.com>
Link: https://lore.kernel.org/r/20200618093616.164413-1-ascull@google.com