MIPS: dts: loongson: drop incorrect dwmac fallback compatible

Device binds to proper PCI ID (LOONGSON, 0x7a03), already listed in DTS,
so checking for some other compatible does not make sense.  It cannot be
bound to unsupported platform.

Drop useless, incorrect (space in between) and undocumented compatible.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>