octeontx2-af: cn10k: Add RPM Rx/Tx stats support

RPM supports below list of counters as an extension to existing counters
 *  class based flow control pause frames
 *  vlan/jabber/fragmented packets
 *  fcs/alignment/oversized error packets

This patch adds support to display supported RPM counters via debugfs
and define new mbox rpm_stats to read all support counters.

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