[SCSI] zfcp: fix adapter initialization

Fixed various problems in opening sequence of adapters which was previously
changed with NPIV support:
o corrected handling when exchange port data function is not supported,
  otherwise adapters on z900 cannot be opened anymore
o corrected setup of timer for exchange port data if called from error
  recovery
o corrected check of return code of exchange config data

Signed-off-by: Andreas Herrmann <aherrman@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>