mmc: mtk-sd: Use BIT() and GENMASK() macros to describe fields

mmc: mtk-sd: Use BIT() and GENMASK() macros to describe fields

Register fields are currently represented with open-coded bit
shifting: replace all occurrences of that to make use of kernel
provided macros BIT and GENMASK to increase human readability.

This patch provides no functional change.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20211216125748.179602-2-angelogioacchino.delregno@collabora.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>