bcma: add mips driver

This adds a mips driver to bcma. This is only found on embedded
devices. For now the driver just initializes the irqs used on this
system.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>