x86: cpu: make sure number of addressable IDs for processor cores meets the spec

Accourding Intel's CPUID[EAX=04H] resulting bits 31 - 26 in EAX
should be:
"
 **** The nearest power-of-2 integer that is not smaller than (1 + EAX[31:26]) is the number of unique
    Core_IDs reserved for addressing different processor cores in a physical package. Core ID is a subset of
    bits of the initial APIC ID.
"

ensure that values stored in EAX[31-26] always meets this condition.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220524151020.2541698-2-imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>