arm64: zynqmp: Describe bus-width for SD card on KV260

SD card is connected with 4 data lines which should be described properly.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/b4046d2f593047400c190e438fd9d05128c293d9.1683034376.git.michal.simek@amd.com