roms: build u-boot *before* checking ubootelf

the current check is flawed, because if u-boot doesn't
exist, but a given build would be the file verified by
the first check, the check would still fail even after
then building u-boot.

building it first will make this check pass, under such
a condition.

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/roms

@@ -141,9 +141,9 @@ add_payloads()
 	[ "$payload_uboot" = "y" ] || return 0
 
 	# add u-boot payload
+	x_ ./update trees -b u-boot $board
 	ubdir="elf/u-boot/$board/$uboot_config"; ubootelf="$ubdir/u-boot.elf" \
 	    && [ ! -f "$ubootelf" ] && ubootelf="$ubdir/u-boot"
-	x_ ./update trees -b u-boot $board
 	[ -f "$ubootelf" ] || $err "$board: Can't find u-boot"
 
 	cbfs "$tmprom" "$ubootelf" "fallback/payload"