net: freescale: ucc_geth: Simplify frame length check

net: freescale: ucc_geth: Simplify frame length check

The frame length check is configured when the phy interface is setup.
However, it's configured according to an internal flag that is always
false. So, just make so that we disable the relevant bit in the MACCFG2
register upon accessing it for other MAC configuration operations.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>