ANDROID: KVM: arm64: Add order to kvm_hyp_memcache

Soon, The host(and guests) will need to allocate contiguous memory
for IOMMU usage, we can extended  memcache to be able to hold different
pages order.
This can be done by encoding the order in the least significant
bits on the head, as pages are at least PAGE_SIZE aligned.

Bug: 277989609
Bug: 278749606
Change-Id: I92b1cf8b653f7e09d8f8c94a4ee7b5adbc87ebdb
Signed-off-by: Mostafa Saleh <smostafa@google.com>