rb532: image: fix broken ifneq statement

Fixes the following build error:

  /devel/openwrt/staging_dir/host/bin/patch-cmdline \
  /devel/openwrt/build_dir/target-mipsel_uClibc-0.9.33.2/linux-rb532/vmlinux-initramfs \
  'root=/dev/mtdblock1 rootfstype=yaffs2 '
  Could not open kernel imagemake[5]: *** [install] Error 255

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 38157