KVM: X86: Move CR0 pdptr_bits into header file as X86_CR0_PDPTR_BITS

Not functionality changed.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20211108124407.12187-7-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>