arm64: Define VM platform for SDM845

Define VM platform config for SDM845. This config is
used for enabling virtual machine on SDM845.
Change-Id: I7298715f881015bd91e88c1d29cbd13c4dc9d517
Signed-off-by: Minming Qi <mqi@codeaurora.org>
Signed-off-by: zhaochen <zhaochen@codeaurora.org>