x86/apic: Rename variables and functions related to x86_io_apic_ops

x86/apic: Rename variables and functions related to x86_io_apic_ops

The names of x86_io_apic_ops and its two member variables are
misleading:

The ->read() member is to read IO_APIC reg, while ->disable()
which is called by native_disable_io_apic()/irq_remapping_disable_io_apic()
is actually used to restore boot IRQ mode, not to disable the IO-APIC.

So rename x86_io_apic_ops to 'x86_apic_ops' since it doesn't only
handle the IO-APIC, but also the local APIC.

Also rename its member variables and the related callbacks.

Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: douly.fnst@cn.fujitsu.com
Cc: joro@8bytes.org
Cc: prarit@redhat.com
Cc: uobergfe@redhat.com
Link: http://lkml.kernel.org/r/20180214054656.3780-6-bhe@redhat.com
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>