sdhci: add warnings for bad buffers in ADMA path

The ADMA code path assumes that the 3 byte alignment fix doesn't cross
a page boundary. I'm not convinced this is worth supporting, but at
least print a warning in the off chance we'll actually see such a request.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/host/sdhci.c

@@ -389,6 +389,7 @@ static int sdhci_adma_table_pre(struct sdhci_host *host,
 		if (offset) {
 			if (data->flags & MMC_DATA_WRITE) {
 				buffer = sdhci_kmap_atomic(sg, &flags);
+				WARN_ON(((long)buffer & PAGE_MASK) > (PAGE_SIZE - 3));
 				memcpy(align, buffer, offset);
 				sdhci_kunmap_atomic(buffer, &flags);
 			}
@@ -510,6 +511,7 @@ static void sdhci_adma_table_post(struct sdhci_host *host,
 				size = 4 - (sg_dma_address(sg) & 0x3);
 
 				buffer = sdhci_kmap_atomic(sg, &flags);
+				WARN_ON(((long)buffer & PAGE_MASK) > (PAGE_SIZE - 3));
 				memcpy(buffer, align, size);
 				sdhci_kunmap_atomic(buffer, &flags);