net: dsa: qca8k: limit port5 delay to qca8337

Limit port5 rx delay to qca8337. This is taken from the legacy QSDK code
that limits the rx delay on port5 to only this particular switch version,
on other switch only the tx and rx delay for port0 are needed.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>