octeontx2-af: cn10kb: Add RPM_USX MAC support

OcteonTx2's next gen platform the CN10KB has RPM_USX MAC which has a
different serdes when compared to RPM MAC. Though the underlying
HW is different, the CSR interface has been designed largely inline
with RPM MAC, with few exceptions though. So we are using the same
CGX driver for RPM_USX MAC as well and will have a different set of APIs
for RPM_USX where ever necessary.

The RPM and RPM_USX blocks support a different number of LMACS.
RPM_USX support 8 LMACS per MAC block whereas legacy RPM supports only 4
LMACS per MAC. with this RPM_USX support double the number of DMAC filters
and fifo size.

This patch adds initial support for CN10KB's RPM_USX  MAC i.e registering
the driver and defining MAC operations (mac_ops). Adds the logic to
configure internal loopback and pause frames and assign FIFO length to
LMACS.

Kernel reads lmac features like lmac type, autoneg, etc from shared
firmware data this structure only supports 4 lmacs per MAC, this patch
extends this structure to accommodate 8 lmacs.

Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>