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/tricorder.h b/include/configs/tricorder.h
index 00d02e8..5859a73 100644
--- a/include/configs/tricorder.h
+++ b/include/configs/tricorder.h
@@ -201,7 +201,7 @@
 		"run nandargs; " \
 		"run loaduimage_ubi; " \
 		"bootm ${loadaddr}\0" \
-	"autoboot=if mmc rescan ${mmcdev}; then " \
+	"autoboot=mmc dev ${mmcdev}; if mmc rescan; then " \
 			"if run loadbootscript; then " \
 				"run bootscript; " \
 			"else " \