[SCSI] qla4xxx: don't free NULL dma pool

The error path calls dma_pool_free() on this path but "chap_table" is
NULL and "chap_dma" is uninitialized.  It's cleaner to just return
directly.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>