ARM: 6058/1: Add support for PCI domains

This patch adds support for PCI domains on ARM platforms.

Also, protect asm/mach/pci.h from multiple inclustions, otherwise
build fails because of pci_domain_nr() and pci_proc_domain()
redefinitions.

Signed-off-by: Anton Vorontsov <avorontsov@mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>