[SCSI] qla2xxx: Cleanse memory allocation logic during probe.

- Drop loop-till-allocated structure of code within
  qla2x00_mem_alloc().
- Properly unwind deallcations of memory during failures.
- Drop qla2x00_allocate_sp_pool() and qla2x00_free_sp_pool()
  functions as their implementations can easily be collapsed into
  the callers.
- Defer DMA pool allocation of SFP data until requested.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>