Add support for the controller present on the AM64x SoC.

There are instances:
sdhci0: 8bit bus width, max 400 MBps
sdhci1: 4bit bus width, max 100 MBps
Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Link: https://lore.kernel.org/r/20210113115908.3882-3-a-govindraju@ti.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>