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 bits case will also fail for the same reason.

Simplify code and remove some dead code accordingly.

[1]: https://lkml.org/lkml/2021/6/7/398Signed-off-by: NChristophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/ef548716606f257939df9738a801f15b6edf2568.1641743405.git.christophe.jaillet@wanadoo.frSigned-off-by: NJakub Kicinski <kuba@kernel.org>