blockdev: Fix regression in -drive if=scsi,index=N
Before commit
622b520f, index=12 meant bus=1,unit=5.
Since the commit, it means bus=0,unit=12. The drive is created, but
not the guest device. That's because the controllers we use with
if=scsi drives (lsi53c895a and esp) support only 7 units, and
scsi_bus_legacy_handle_cmdline() ignores drives with unit numbers
exceeding that limit.
Changing the mapping of index to bus, unit is a regression. Breaking
-drive invocations that used to work just makes it worse.
Revert the part of commit
622b520f that causes this, and clean up
some.
Note that the fix only affects if=scsi. You can still put more than 7
units on a SCSI bus with -device & friends.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>