The MV88E6097 chip does not support configuring jumbo frames. Prior to
commit 5f436666 only the 6352, 6351, 6165 and 6320 chips configured
jumbo mode. The refactor accidentally added the function for the 6097.
Remove the erroneous function pointer assignment.

Fixes: 5f436666 ("net: dsa: mv88e6xxx: Refactor setting of jumbo frames")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>