ipq40xx: add uboot-envtools to default packages

ipq40xx: add uboot-envtools to default packages

When support for Luma WRTQ-329ACN was added, the instructions for
flashing this device include using tools from uboot-envtools package.
Unfortunately the OpenWrt buildroot system omits packages from
DEVICE_PACKAGES when CONFIG_TARGET_MULTI_PROFILE,
CONFIG_TARGET_PER_DEVICE_ROOTFS, CONFIG_TARGET_ALL_PROFILES are set. In
result the official images are without tools mentioned in the
instruction. The workoround for the fashing would be installing
uboot-envtools when booted with initramfs image, but not always the
access to internet is available. The other method would be to issue the
necesary command in U-Boot environment but some serial terminals default
configuration don't work well with pasting lines longer than 80 chars.
Therefore add uboot-envtools to default packages, which adds really
small flash footprint to rootfs, where increased size usually is not an
issue.

Signed-off-by: Tomasz Maciej Nowak <tmn505@gmail.com>