arm64: dts: ti: k3-j7200-main: Add support for MMC/SD controller nodes

Add support for MMC/SD controller nodes present on TI's j7200 SoCs.

There are two nodes:
        1. sdhci0 (8 bit bus width, 200 MHz, HS200, 200 MBps)
        2. sdhci1 (4 bit bus width, 50 MHz, HS, 25 MBps)

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Tested-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Sekhar Nori <nsekhar@ti.com>
Link: https://lore.kernel.org/r/20200924112644.11076-2-faiz_abbas@ti.com