octeontx2-pf: Prepare for QOS offload

This patch moves rate limiting definitions to a common header file and
adds csr definitions required for QOS code.

Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>