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_beagle.h b/include/configs/omap3_beagle.h
index f79f996..7a3cc16 100644
--- a/include/configs/omap3_beagle.h
+++ b/include/configs/omap3_beagle.h
@@ -289,7 +289,7 @@
 	"userbutton_nonxm=gpio input 7;\0"
 /* "run userbutton" will return 1 (false) if is pressed and 0 (false) if not */
 #define CONFIG_BOOTCOMMAND \
-	"if mmc rescan ${mmcdev}; then " \
+	"mmc dev ${mmcdev}; if mmc rescan; then " \
 		"if run userbutton; then " \
 			"setenv bootenv uEnv.txt;" \
 		"else " \