x86: apic - unify setup_local_APIC

- remove useless read of APIC_LVR
- wrap with preempt_disable/enable
- check for integrated APIC just in place

v2: fix by Yinghai Lu.
	fix lapic_is_integrated using
	let 64-bit too have pic_mode

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>