x86: Fix APIC MSR constant names

x86: Fix APIC MSR constant names

We currently have MSR_IA32_APICBASE and MSR_IA32_APICBASE_MSR which are
synonymous from a naming point of view, but refer to very different things.

Rename the x2APIC MSRs to MSR_X2APIC_*, which are shorter constants and
visually separate the register function from the generic APIC name.  For the
case ranges, introduce MSR_X2APIC_LAST, rather than relying on the knowledge
that there are 0x3ff MSRs architecturally reserved for x2APIC functionality.

For functionality relating to the APIC_BASE MSR, use MSR_APIC_BASE for the MSR
itself, but drop the MSR prefix from the other constants to shorten the names.
In all cases, the fact that we are dealing with the APIC_BASE MSR is obvious
from the context.

No functional change (the combined binary is identical).

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>