x86: nSVM: Check #OF exception handling in L2

Add coverage for OF exception handling in L2 when only L2 OF
exception handler is registered.

OF exception generated using instrumented code and it is handled
by L2 OF exception handler.

Signed-off-by: Manali Shukla <manali.shukla@amd.com>
Message-Id: <20211229062201.26269-4-manali.shukla@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>