net: stmmac: Fix incorrect memcpy source memory

The memcpy() currently copies mdio_bus_data into new_bus->irq, which
makes no sense, since the mdio_bus_data structure contains more than
just irqs. The code was likely supposed to copy mdio_bus_data->irqs
into the new_bus->irq instead, so fix this.

Fixes: e7f4dc35

 ("mdio: Move allocation of interrupts into core")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>