KVM: MMU: Ignore reserved bits in cr3 in non-pae mode

This patch removes the fault injected when the guest attempts to set reserved
bits in cr3.  X86 hardware doesn't generate a fault when setting reserved bits.
The result of this patch is that vmware-server, running within a kvm guest,
boots and runs memtest from an iso.

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>