bcma: detect PCI core working in hostmode

We must not init it like clientmode one, it would break device (tested
by Hauke on BCM4718). Add stub hostmode driver for now.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>