[SCSI] ibmvfc: Miscellaneous fixes

Properly setup the size of the async event queue. This fixes a bug where async events
were not getting processed by the driver.

Setup target_id field in the driver's target struct so that target sysfs attributes
work for multiple targets.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>