scsi: hisi_sas: Remove useless DMA-32 fallback configuration

scsi: hisi_sas: Remove useless DMA-32 fallback configuration

As stated in [1], dma_set_mask() with a 64-bit mask never fails if
dev->dma_mask is non-NULL. So, if it fails, the 32-bit case will also fail
for the same reason.

Simplify code and remove some dead code accordingly.

[1]: https://lore.kernel.org/linux-kernel/YL3vSPK5DXTNvgdx@infradead.org/#t

Link: https://lore.kernel.org/r/1bf2d3660178b0e6f172e5208bc0bd68d31d9268.1642237482.git.christophe.jaillet@wanadoo.fr
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>