x86: nSVM: Check #BP exception handling in L2

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

BP exception is generated using int3 instruction and it is handled
by L2 BP exception handler.

Signed-off-by: Manali Shukla <manali.shukla@amd.com>
Message-Id: <20211229062201.26269-3-manali.shukla@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>