smegw01: Pass 'mmcpart' to the kernel command line

When using SWUpdate, it is necessary to toggle between partitions.

Use the 'mmcpart' environment variable to accomplish that.
Signed-off-by: NFabio Estevam <festevam@denx.de>

include/configs/smegw01.h

@@ -26,9 +26,8 @@
 	"bootm_size=0x10000000\0" \
 	"mmcdev=0\0" \
 	"mmcpart=1\0" \
-	"mmcroot=/dev/mmcblk0p1 rootwait rw\0" \
 	"mmcargs=setenv bootargs console=${console},${baudrate} " \
-		"root=${mmcroot}\0" \
+		"root=/dev/mmcblk0p${mmcpart} rootwait rw\0" \
 	"loadimage=load mmc ${mmcdev}:${mmcpart} ${loadaddr} boot/${image}\0" \
 	"loadfdt=load mmc ${mmcdev}:${mmcpart} ${fdt_addr} boot/${fdtfile}\0" \
 	"mmcboot=echo Booting from mmc ...; " \