km/common: use u-boot.kwb for u-boot update function on arm

Now we use the standard u-boot make to build the Kirkwood binary.
The output file is u-boot.kwb. So use this name for the tftp
update function to avoid confusion, because this is the binary we
need on Kirkwood.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
cc: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <wd@denx.de>
diff --git a/include/configs/km/km-powerpc.h b/include/configs/km/km-powerpc.h
index 4cec57c..7610358 100644
--- a/include/configs/km/km-powerpc.h
+++ b/include/configs/km/km-powerpc.h
@@ -75,6 +75,7 @@
 		"cramfsload ${fdt_addr_r} "				\
 		"fdt_0x${IVM_BoardId}_0x${IVM_HWKey}.dtb\0"		\
 	"fdt_addr_r=" xstr(CONFIG_KM_FDT_ADDR) "\0"			\
+	"u-boot="xstr(CONFIG_HOSTNAME) "/u-boot.bin\0"			\
 	"update="							\
 		"protect off " xstr(BOOTFLASH_START) " +${filesize} && "\
 		"erase " xstr(BOOTFLASH_START) "  +${filesize} && "	\