ANDROID: kvm: pkvm: Implement check_emulate_instruction

The check_emulate_instruction callback can be used by the host KVM
during emulating a MMIO instruction. For the npVM, returning
X86EMUL_CONTINUE is good enough. For the pVM, this is not expected if
the pVM is enlightened by using hypercall to access MMIO. And if the pVM
still expects receiving #VE, returning X86EMUL_RETRY_INSTR can let the
pVM to retry after clearing the suppress #VE bit in the EPT.

Bug: 391539939
Test: pKVM works
Upstream-Task: 402758258

Change-Id: I4d0a7736ffad96702985c434064c3585f6a95d24
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Signed-off-by: Dmytro Maluka <dmaluka@google.com>