drivers: ethernet: adin2111: always append crc32 to the eth frame

Enable appending of a crc32 at the end of the frame by the MAC,
always. This is always needed since the driver is not adding it.

This field has nothing to do with Generic SPI protocol-related
8-bit CRC, so this patch removes the CONFIG_ETH_ADIN2111_SPI_CFG0
choice related to this setting.

Testing without this flag set, packets are not forwareded in the
network, since the driver is not appending any crc32 header
to the frame.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>