octeontx2-af: RPM: fix stale RSFEC counters

The earlier patch sets the 'Stats control register' for RPM
receive/transmit statistics instead of RSFEC statistics,
causing the driver to return stale FEC counters.

Fixes: 84ad3642 ("octeontx2-af: Add FEC stats for RPM/RPM_USX block")
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>