ssb: Fix initcall ordering

ssb must init after PCI but before the ssb drivers.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: Christian Casteyde <casteyde.christian@free.fr>
Fixes-bug: #9219
Signed-off-by: John W. Linville <linville@tuxdriver.com>