mmc: dw_mmc: add a quirk for accessing 64-bit FIFOs in two halves

[ Upstream commit 57c0902f ]

In certain DW MMC implementations (such as in some Exynos7870
controllers), 64-bit read/write is not allowed from a 64-bit FIFO.
Add a quirk which facilitates accessing the 64-bit FIFO registers in two
32-bit halves.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Link: https://lore.kernel.org/r/20250219-exynos7870-mmc-v2-2-b4255a3e39ed@disroot.org


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>