IOCB BDE not getting fully initialized during reuse

Symptoms: Driver gets Status 3 and Reason 0x13 on IOCB completions.

Cause: The IOCB bpl.bdeSize and bdeFlags are not getting initialized on reuse.

Fix: Reinitialize these fields in prep_dma each time an IOCB is used.
Signed-off-by: James Smart <James.Smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>