M28: Fix the use of gpmi-nand in mtdparts

The mtd name of the NAND in Linux is "gpmi-nand", not "gpmi-nand.0" as
it would be expected, since the controller doesn't support multiple NANDs
attached to it as of now. Rectify this flub by adjusting default mtdparts.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Acked-by: Stefano Babic <sbabic@denx.de>

include/configs/m28evk.h

@@ -171,9 +171,9 @@
 #define	CONFIG_LZO
 #define	CONFIG_MTD_DEVICE
 #define	CONFIG_MTD_PARTITIONS
-#define	MTDIDS_DEFAULT			"nand0=gpmi-nand.0"
+#define	MTDIDS_DEFAULT			"nand0=gpmi-nand"
 #define	MTDPARTS_DEFAULT			\
-	"mtdparts=gpmi-nand.0:"			\
+	"mtdparts=gpmi-nand:"			\
 		"3m(bootloader)ro,"		\
 		"512k(environment),"		\
 		"512k(redundant-environment),"	\