spi: mediatek: add mtk_spi_compatible support

this patch adds max_fifo_size and must_rx compat support.

Signed-off-by: Leilk Liu <leilk.liu@mediatek.com>
Link: https://lore.kernel.org/r/20210322055244.30179-4-leilk.liu@mediatek.com


Signed-off-by: Mark Brown <broonie@kernel.org>