x86/apic: Get rid of apic_phys

x86/apic: Get rid of apic_phys

No need for an extra variable to find out whether the APIC has been mapped
or is accessible (X2APIC mode).

Provide an inline for this and check apic_mmio_base which is only set when
the local APIC has been mapped.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Juergen Gross <jgross@suse.com> # Xen PV (dom0 and unpriv. guest)