ANDROID: pkvm: implement memory mapped I/O emulation

Add MMIO emulation handling logic. When host VM-exit for a tracked
memory mapped I/O, use a simple instruction decoder to parse the
MMIO instruction and wrap it into an MMIO access request. Because
host only use simple mov instruction for mmcfg region access, the
instruction decoder for now only decodes simple mov instructions.
If a proper handler is found in the MMIO emulation table, call the
handler to emulate the MMIO access.

Signed-off-by: Tinghao Zhang <tinghao.zhang@intel.com>

Bug: 349990461
Test: Android can run protected VMs

Change-Id: Ic067abce7b9870765d9e517a4775e006e0754980
Signed-off-by: Dmytro Maluka <dmaluka@google.com>