ANDROID: KVM: arm64: Move hyp_memcache flags within the struct

With the introduction of the pKVM hyp allocator, memcaches for VMs and
vCPUs are now only used for carrying pages dedicated to the stage-2.
With specialized memcaches, it is easy to change the API so the
flags are attached to the memcache, simplifying the job for the callers.

Bug: 278749606
Bug: 273748186
Change-Id: I680cc02ebc81955529b8260e5f0ef43b5a112880
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>