ARM: sheevaplug: unbreak kernel bootargs / mtdparts command by dropping double mtdparts=

Commit 1e3d640316 (ARM: sheevaplug: redefine MTDPARTS) prepended mtdparts=
to the flash partition information in CONFIG_MTDPARTS, but it is used like
"mtdparts=" CONFIG_MTDPARTS - So we end up passing mtdparts=mtdparts=.. to
the kernel, confusing the cmdline partition parser.

Fix it by dropping the double 'mtdparts='.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

include/configs/sheevaplug.h

@@ -63,7 +63,7 @@
 	"${x_bootcmd_usb}; bootm 0x6400000;"
 
 #define CONFIG_MTDPARTS		\
-	"mtdparts=orion_nand:512K(uboot),"				\
+	"orion_nand:512K(uboot),"				\
 	"512K(env),1M(script),6M(kernel),"				\
 	"12M(ramdisk),4M(spare),-(rootfs)\0"