MFC rev. 197462:

MFC rev. 197462:
Do not call BUS_DRIVER_ADDED() for detached buses (attach failed) on
driver load. This fixes crash on atapicam module load on systems, where
some ata channels (usually ata1) was probed, but failed to attach.

Reviewed by:    jhb, imp
Tested by:      many
Approved by:    re (kib)

git-svn-id: svn://svn.freebsd.org/base/stable/8@197494 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f