KVM: x86: Remove debug assertion of non-PAE reserved bits

Commit 346874c9 ("KVM: x86: Fix CR3 reserved bits") removed non-PAE
reserved bits which were not according to Intel SDM.  However, residue was left
in a debug assertion (CR3_NONPAE_RESERVED_BITS).  Remove it.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>