mmc: Fixes for Dual Data Rate (DDR) support

The DDR support patch needs the following fixes:

- The block driver does not need to know about DDR, any more
  than it needs to know about bus width.
- Not only the card must be switched to DDR mode.  The host
  controller must also be configured, which is done through
  the 'set_ios()' function.
- Do not set the DDR mode state until after the switch command
  is successful.
- Setting block length is not supported in DDR mode.  Make that
  a core function and change the other place it is used (mmc_test)
  also.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

include/linux/mmc/host.h

@@ -50,6 +50,11 @@ struct mmc_ios {
 #define MMC_TIMING_LEGACY	0
 #define MMC_TIMING_MMC_HS	1
 #define MMC_TIMING_SD_HS	2
+
+	unsigned char	ddr;			/* dual data rate used */
+
+#define MMC_SDR_MODE		0
+#define MMC_DDR_MODE		1
 };
 
 struct mmc_host_ops {