mshv: Add support for a new parent partition configuration

mshv: Add support for a new parent partition configuration

Detect booting as an "L1VH" partition. This is a new scenario very
similar to root partition where the mshv_root driver can be used to
create and manage guest partitions.

It mostly works the same as root partition, but there are some
differences in how various features are handled. hv_l1vh_partition()
is introduced to handle these cases. Add hv_parent_partition()
which returns true for either case, replacing some hv_root_partition()
checks.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>