spi: mediatek: use correct SPI_CFG2_REG MACRO

[ Upstream commit 44b37eb79e16a56cb30ba55b2da452396b941e7a ]

this patch use correct SPI_CFG2_REG offset.

Signed-off-by: leilk.liu <leilk.liu@mediatek.com>
Link: https://lore.kernel.org/r/20200701090020.7935-1-leilk.liu@mediatek.com


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