validation: packet: do not account for head or tail room in packet length computations
validation: packet: do not account for head or tail room in packet length computations

It is the pool responsibility to ensure that there is enough space available for headroom and tailroom in the segment(s)
Also fixes the issue where ODP_CONFIG_PACKET_SEG_MIN_LEN < ODP_CONFIG_PACKET_HEADROOM

Signed-off-by: Nicolas Morey-Chaisemartin <7188b998d7bb37a035517aa285fa3f5a95344e80@kalray.eu>
Reviewed-and-tested-by: Bill Fischofer <52f3c909d51cc5d355a68a403df6906b3c1a8f83@linaro.org>
Signed-off-by: Maxim Uvarov <db4d16e02ae2d7493db430203537da8b2e34f290@linaro.org>

rsalveti/odp,nmorey/odp,dkrot/odp,dkrot/odp,kalray/odp-mppa,kalray/odp-mppa,nmorey/odp,mike-holmes-linaro/odp,kalray/odp-mppa,kalray/odp-mppa,erachmi/odp,erachmi/odp,erachmi/odp,rsalveti/odp,dkrot/odp,ravineet-singh/odp,nmorey/odp,mike-holmes-linaro/odp,rsalveti/odp,mike-holmes-linaro/odp,rsalveti/odp,nmorey/odp,erachmi/odp,dkrot/odp,kalray/odp-mppa,mike-holmes-linaro/odp,ravineet-singh/odp,kalray/odp-mppa,kalray/odp-mppa,ravineet-singh/odp,rsalveti/odp,ravineet-singh/odp