[SCSI] zfcp: Remove busid macro

With the change to the dev_ message macros, the macro to get the busid
is only used in a few places. Remove it and directly get the dev_name
from the device.

Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>