scsi: qla2xxx: use lower_32_bits and upper_32_bits instead of reinventing them

This also moves the optimization for builds with 32-bit dma_addr_t to
the compiler (where it belongs) instead of opencoding it based on
incorrect assumptions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>