sfc: SFX7101: Remove workaround for bad link training

Early versions of the SFX7101 firmware could complete link training in
a state where it would not adequately cancel noise (Solarflare bug
10750).  We previously worked around this by resetting the PHY after
seeing many Ethernet CRC errors.  This workaround is unsafe since it
takes no account of the interval between errors; it also appears to
be unnecessary with production firmware.  Therefore remove it.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>