KVM: x86: SVM: fix avic spec based definitions again

Due to wrong rebase, commit
4a204f78

 ("KVM: SVM: Allow AVIC support on system w/ physical APIC ID > 255")

moved avic spec #defines back to avic.c.

Move them back, and while at it extend AVIC_DOORBELL_PHYSICAL_ID_MASK to 12
bits as well (it will be used in nested avic)

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220322172449.235575-5-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>