octeontx2-pf: move lmt flush to include/linux/soc

On OcteonTX2 platform CPT instruction enqueue and NIX
packet send are only possible via LMTST operations which
uses LDEOR instruction. This patch moves lmt flush
function from OcteonTX2 nic driver to include/linux/soc
since it will be used by OcteonTX2 CPT and NIC driver for
LMTST.

Signed-off-by: Suheil Chandran <schandran@marvell.com>
Signed-off-by: Srujana Challa <schalla@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>