x86: dtb: Add early parsing of IO_APIC

APIC and IO_APIC have to be added to the system early because
native_init_IRQ() requires it.

In order to obtain the address of the ioapic the device tree has to be
unflattened so of_address_to_resource() works.

The device tree is relocated to ensure it is always covered by the
kernel mapping. That way the boot loader does not have to make
any assumptions about kernel's memory layout.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: sodaville@linutronix.de
Cc: devicetree-discuss@lists.ozlabs.org
Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
LKML-Reference: <1298405266-1624-6-git-send-email-bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>