mshv: Use common "entry virt" APIs to do work in root before running guest

mshv: Use common "entry virt" APIs to do work in root before running guest

Use the kernel's common "entry virt" APIs to handle pending work prior to
(re)entering guest mode, now that the virt APIs don't have a superfluous
dependency on KVM.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>