mmc: core: stop trying to switch width when only one bit is supported

mmc_select_bus_width() will try to switch to MMC_BUS_WIDTH_4 even if
MMC_CAP_4_BIT_DATA and MMC_CAP_8_BIT_DATA are not set in host->caps.
Return as soon as possible when those flags are not set

Fixes: 577fb13199b1 (mmc: rework selection of bus speed mode)
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: <stable@vger.kernel.org> # 3.17
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/mmc.c

@@ -886,7 +886,7 @@ static int mmc_select_bus_width(struct mmc_card *card)
 	unsigned idx, bus_width = 0;
 	int err = 0;
 
-	if (!mmc_can_ext_csd(card) &&
+	if (!mmc_can_ext_csd(card) ||
 	    !(host->caps & (MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA)))
 		return 0;