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.

So if dma_set_mask_and_coherent() succeeds, 'netdev->features' will have
NETIF_F_HIGHDMA in all cases. Move the assignment of this feature in
be_netdev_init() instead be_probe() which is a much logical place.

Simplify code and remove some dead code accordingly.

[1]: https://lkml.org/lkml/2021/6/7/398Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/637696d7141faa68c29fc34b70f9aa67d5e605f0.1641718999.git.christophe.jaillet@wanadoo.frSigned-off-by: Jakub Kicinski <kuba@kernel.org>