ARM: sheevaplug: drop unneded 'usb start' from boot command

The default bootcommand executes x_bootcmd_usb AFTER loading a kernel from
nand and just before executing it, which only slows down boot without adding
any functionality - So drop it.

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

include/configs/sheevaplug.h

@@ -60,7 +60,7 @@
  */
 #define CONFIG_BOOTCOMMAND		"${x_bootcmd_kernel}; "	\
 	"setenv bootargs ${x_bootargs} ${x_bootargs_root}; "	\
-	"${x_bootcmd_usb}; bootm 0x6400000;"
+	"bootm 0x6400000;"
 
 #define CONFIG_MTDPARTS		\
 	"orion_nand:512K(uboot),"				\