net: dsa: b53: Fixup endianness warnings

leX_to_cpu() expects to be passed an __leX type.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>