cpcihp_generic: prevent loading without "bridge" parameter

cpcihp_generic module requires configured "bridge" module parameter.
But it can be loaded successfully without that parameter.
Because module init call ends up returning positive value.

This patch prevents from loading without setting "bridge" module parameter.

Signed-off-by: Akinbou Mita <akinobu.mita@gmail.com>
Signed-off-by: Scott Murray <scottm@somanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>