mmc: mtk-sd: Clarify patch bit register initialization and layout

mmc: mtk-sd: Clarify patch bit register initialization and layout

In preparation for cleaning up the msdc_init_hw register setting
for the patch bit registers, add the necessary definitions for
bits in the MSDC_PATCH_BIT and MSDC_PATCH_BIT1 registers and use
them in place of "magic numbers" writes during initialization.

This commit brings no functional differences.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20250325110701.52623-2-angelogioacchino.delregno@collabora.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>