octeontx2-af: Use DMA_ATTR_FORCE_CONTIGUOUS attribute in DMA alloc

CN10K platform requires physically contiguous memory for LMTST
operations which goes beyond a single page. Not having physically
contiguous memory will result in HW fetching transmit descriptors from
a wrong memory location.

Hence use DMA_ATTR_FORCE_CONTIGUOUS attribute while allocating
LMTST regions.

Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>