drivers: ethernet: adin2111: fix generic spi withotut crc8 mode

After some debugging related to non-working "Generic SPI without CRC"
mode in eval_adin2111_ebz (CONFIG_ETH_ADIN2111_SPI_CFG0=n), noticed
that even after proper STATUS0 RESETC bit detection, registers,
for a certain period (some msecs) still reads as zero.

This patch fixes adin2111_await_device and with it the
"Generic SPI without CRC" mode.

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