On boards like the sama5d27 som1 ek, we have two SD card slots, so error
messages are more useful if they refer to the SDHCI instance. We didn't
do this at first, because the common code is compiled for PBL as well.
With a sprinkle of preprocessor ifdeffery, we can have both.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>