scsi: zfcp: clean up no longer existent prototype from zfcp API header

Commit a54ca0f6

 ("[SCSI] zfcp: Redesign of the debug tracing for HBA
records.") refactored zfcp_dbf_hba_berr into zfcp_dbf_hba_bit_err
but added the prototype for the latter without removing it for the former.

Suggested-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>