KVM: x86: do mask out upper bits of PAE CR3

KVM: x86: do mask out upper bits of PAE CR3

This reverts the change of commit 0239943497961cdb05404c1542b9a4f307f20056,
as the behavior it modified was intended.

The VM is running in 32-bit PAE mode, and Table 4-7 of the Intel manual
says:

Table 4-7. Use of CR3 with PAE Paging
Bit Position(s)	Contents
4:0		Ignored
31:5		Physical address of the 32-Byte aligned
		page-directory-pointer table used for linear-address
		translation
63:32		Ignored (these bits exist only on processors supporting
		the Intel-64 architecture)

To placate the static checker, write the mask explicitly as an
unsigned long constant instead of using a 32-bit unsigned constant.

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 0239943497961cdb05404c1542b9a4f307f20056
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>