[POWERPC] Add Marvell mv64x60 PCI bridge support

This patch adds PCI bridge support for the Marvell mv64x60 chip.
We also provide the ability to read/write the mv64x60 hotswap
register via sysfs if the hs_reg_valid property is set in the
device tree.

Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>