MIPS: generic: Fix NI 169445 its build

Since commit 04a85e087a ("MIPS: generic: Move NI 169445 FIT image
source to its own file"), a generic 32r2el_defconfig kernel fails to
build with the following build error:

  ITB     arch/mips/boot/vmlinux.gz.itb
Error: arch/mips/boot/vmlinux.gz.its:111.1-2 syntax error
FATAL ERROR: Unable to parse input tree
mkimage Can't read arch/mips/boot/vmlinux.gz.itb.tmp: Invalid argument

Fix arch/mips/generic/board-ni169445.its.S to include the necessary "/"
node path before the first open brace.

The original issue in arch/mips/generic/vmlinux.its.S was fixed directly
in the original commit 7aacf86b75 ("MIPS: NI 169445 board support")
after https://patchwork.linux-mips.org/patch/16941/ was submitted, but
the separate its.S file wasn't correctly fixed when resolving the
conflict in commit 04a85e087a ("MIPS: generic: Move NI 169445 FIT
image source to its own file").

Fixes: 04a85e087a ("MIPS: generic: Move NI 169445 FIT image source to its own file")
Signed-off-by: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Nathan Sullivan <nathan.sullivan@ni.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17561/
Signed-off-by: James Hogan <jhogan@kernel.org>

arch/mips/generic/board-ni169445.its.S

@@ -1,4 +1,4 @@
-{
+/ {
 	images {
 		fdt@ni169445 {
 			description = "NI 169445 device tree";