doc: userguide: add user documentation for packet references
doc: userguide: add user documentation for packet references

Signed-off-by: Bill Fischofer <52f3c909d51cc5d355a68a403df6906b3c1a8f83@linaro.org>
Reviewed-by: Balasubramanian Manoharan <affd9aba178b6c6e9aaff69252817fd03d71ae35@linaro.org>
Signed-off-by: Maxim Uvarov <db4d16e02ae2d7493db430203537da8b2e34f290@linaro.org>

dkrot/odp,dkrot/odp,dkrot/odp,dkrot/odp