net/thunderx: check data offset alignment requirement

net/thunderx: check data offset alignment requirement

nicvf HW expects the DMA address of the packet data to be
aligned with cache line size.

Packet data offset is a function of struct mbuf size,
mbuf private size and headroom. mbuf private size can
be changed from the application in pool creation, this
check detects HW alignment requirement constraint in pmd
start function.

Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>