sdhci: use PIO when DMA can't satisfy the request

Some controllers have been designed on the assumption that all transfers
will be 32-bit aligned, both in start address and in size. This is not a
guarantee the SDHCI specification provides and not one we can provide.

Revert back to PIO for individual requests in order to work around the
hardware bug.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/host/sdhci.h

@@ -171,7 +171,8 @@ struct sdhci_host {
 	spinlock_t		lock;		/* Mutex */
 
 	int			flags;		/* Host attributes */
-#define SDHCI_USE_DMA		(1<<0)
+#define SDHCI_USE_DMA		(1<<0)		/* Host is DMA capable */
+#define SDHCI_REQ_USE_DMA	(1<<1)		/* Use DMA for this req. */
 
 	unsigned int		max_clk;	/* Max possible freq (MHz) */
 	unsigned int		timeout_clk;	/* Timeout freq (KHz) */