ARM: PCI: remove unused sys->hw

Some platforms mark their hw_pci structure as __initdata, which means
it will be discarded after init time.  Storing pointers to __initdata
in long lived data structures is a potential source of problems, and
in this case, sys->hw is unused apart from its initialization.

So, lets remove this member and its initializer.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>