KVM: arm64: Remove kvm_host_data_t typedef

The kvm_host_data_t typedef is used inconsistently and goes against the
kernel's coding style. Remove it in favour of the full struct specifier.

Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200915104643.2543892-4-ascull@google.com