octeontx2-af: Add new CGX_CMD to get PHY FEC statistics

This patch adds support to fetch fec stats from PHY. The stats are
put in the shared data struct fwdata.  A PHY driver indicates
that it has FEC stats by setting the flag fwdata.phy.misc.has_fec_stats

Besides CGX_CMD_GET_PHY_FEC_STATS, also add CGX_CMD_PRBS and
CGX_CMD_DISPLAY_EYE to enum cgx_cmd_id so that Linux's enum list is in sync
with firmware's enum list.

Signed-off-by: Felix Manlunas <fmanlunas@marvell.com>
Signed-off-by: Christina Jacob <cjacob@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>