mmc: at91_mci: fix pointer errors

Fixes two pointer errors, one which leads to memory overwrites if used
with large chunks of data.

Signed-off-by: Wolfgang Muees <wolfgang.mues@auerswald.de>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Andrew Victor <avictor.za@gmail.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/at91_mci.c

@@ -227,11 +227,13 @@ static inline void at91_mci_sg_to_dma(struct at91mci_host *host, struct mmc_data
 			for (index = 0; index < (amount / 4); index++)
 				*dmabuf++ = swab32(sgbuffer[index]);
 		} else {
-			memcpy(dmabuf, sgbuffer, amount);
-			dmabuf += amount;
+			char *tmpv = (char *)dmabuf;
+			memcpy(tmpv, sgbuffer, amount);
+			tmpv += amount;
+			dmabuf = (unsigned *)tmpv;
 		}
 
-		kunmap_atomic(sgbuffer, KM_BIO_SRC_IRQ);
+		kunmap_atomic(((void *)sgbuffer) - sg->offset, KM_BIO_SRC_IRQ);
 
 		if (size == 0)
 			break;