net: ethernet: adi: adin1110: Fix SPI transfers

No need to use more than one SPI transfer for reads.
Use only one from now as ADIN1110/2111 does not tolerate
CS changes during reads.

The BCM2711/2708 SPI controllers worked fine, but the NXP
IMX8MM could not keep CS lowered during SPI bursts.

This change aims to make the ADIN1110/2111 driver compatible
with both SPI controllers, without any loss of bandwidth/other
capabilities.

Fixes: bc93e19d

 ("net: ethernet: adi: Add ADIN1110 support")
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Signed-off-by: David S. Miller <davem@davemloft.net>