mmc: sdhci: add quirk for max len ADMA descriptors

Some controllers misparse segment length 0 as being 0, not 65536. Add
a quirk to deal with it.

Signed-off-by: Olof Johansson <olof@lixom.net>
Reviewed-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index d5febe5..9e15f41 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1949,10 +1949,14 @@
 	 * of bytes. When doing hardware scatter/gather, each entry cannot
 	 * be larger than 64 KiB though.
 	 */
-	if (host->flags & SDHCI_USE_ADMA)
-		mmc->max_seg_size = 65536;
-	else
+	if (host->flags & SDHCI_USE_ADMA) {
+		if (host->quirks & SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC)
+			mmc->max_seg_size = 65535;
+		else
+			mmc->max_seg_size = 65536;
+	} else {
 		mmc->max_seg_size = mmc->max_req_size;
+	}
 
 	/*
 	 * Maximum block size. This varies from controller to controller and