net: stmmac: Remove WAKE_MAGIC if HW shows no pmt_magic_frame

Remove WAKE_MAGIC from supported modes if the HW capability register
shows no support for pmt_magic_frame.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>