[ARM] S3C24XX: Documentation: update SD/MMC status

Update SD/MMC status now that the driver is merged.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>

Documentation/arm/Samsung-S3C24XX/Overview.txt

@@ -176,6 +176,17 @@ NAND
   For more information see Documentation/arm/Samsung-S3C24XX/NAND.txt
 
 
+SD/MMC
+------
+
+  The SD/MMC hardware pre S3C2443 is supported in the current
+  kernel, the driver is drivers/mmc/host/s3cmci.c and supports
+  1 and 4 bit SD or MMC cards.
+
+  The SDIO behaviour of this driver has not been fully tested. There is no
+  current support for hardware SDIO interrupts.
+
+
 Serial
 ------