mx6slevk: Remove duplicated "mmc dev" command

The "mmc dev ${mmcdev}" command is done twice.

Remove one ocurrence to avoid the duplication.

Signed-off-by: Fabio Estevam <festevam@denx.de>
diff --git a/configs/mx6slevk_defconfig b/configs/mx6slevk_defconfig
index 12789c9..79057f7 100644
--- a/configs/mx6slevk_defconfig
+++ b/configs/mx6slevk_defconfig
@@ -12,7 +12,7 @@
 # CONFIG_CMD_BMODE is not set
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_USE_BOOTCOMMAND=y
-CONFIG_BOOTCOMMAND="mmc dev ${mmcdev};mmc dev ${mmcdev}; if mmc rescan; then if run loadbootscript; then run bootscript; else if run loadimage; then run mmcboot; else run netboot; fi; fi; else run netboot; fi"
+CONFIG_BOOTCOMMAND="mmc dev ${mmcdev}; if mmc rescan; then if run loadbootscript; then run bootscript; else if run loadimage; then run mmcboot; else run netboot; fi; fi; else run netboot; fi"
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y