kni: remove continuous memory restriction

kni: remove continuous memory restriction

Use mempool buf_addr and buf_physaddr fields for address translation.

Since each mbuf address calculated separately, the restriction of all
mbufs should come from a continuous memory restriction is no more valid.

mbuf related FIFO's content changed, rx_q and alloc_q now carries
physical address of mbufs. tx_q and free_q content not changed, they
still carries virtual address of mbufs.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>