configs: Fix usage of mmc rescan

Fix usage of 'mmc rescan' by many configs.  Proper use is
'mmc dev ${mmcdev}; mmc rescan' to set the mmc device and then rescan
the device.  'mmc rescan' itself does not take any arguments.

Signed-off-by: Andrew Bradford <andrew@bradfordembedded.com>
diff --git a/include/configs/omap3_logic.h b/include/configs/omap3_logic.h
index b975a6c..b2457d0 100644
--- a/include/configs/omap3_logic.h
+++ b/include/configs/omap3_logic.h
@@ -202,7 +202,7 @@
 	"mtdids=" MTDIDS_DEFAULT "\0"	\
 	"mtdparts=" MTDPARTS_DEFAULT "\0" \
 	"mmcdev=0\0" \
-	"autoboot=if mmc rescan ${mmcdev}; then " \
+	"autoboot=mmc dev ${mmcdev}; if mmc rescan; then " \
 			"if run loadbootscript; then " \
 				"run bootscript; " \
 			"else " \