KVM: arm64: Introduce wrappers for host and hyp spin lock accessors

In preparation for adding additional locked sections for manipulating
page-tables at EL2, introduce some simple wrappers around the host and
hypervisor locks so that it's a bit easier to read and bit more difficult
to take the wrong lock (or even take them in the wrong order).

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211215161232.1480836-10-qperret@google.com