kvm: selftests: aarch64: fix some vgic related comments

Fix the formatting of some comments and the wording of one of them (in
gicv3_access_reg).

Signed-off-by: Ricardo Koller <ricarkol@google.com>
Reported-by: Reiji Watanabe <reijiw@google.com>
Cc: Andrew Jones <drjones@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220127030858.3269036-5-ricarkol@google.com