spi: mediatek: add spi support for mt6765 IC

This patch add spi support for mt6765 IC.

Signed-off-by: luhua.xu <luhua.xu@mediatek.com>
Link: https://lore.kernel.org/r/1568195731-3239-3-git-send-email-luhua.xu@mediatek.com


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