net: phy: Fixup GPLv2+ SPDX tags based on license text

A few PHY drivers have the GPLv2+ license text. They then either have
a MODULE_LICENSE() of GPLv2 only, or an SPDX tag of GPLv2 only.

Since the license text is much easier to understand than either the
SPDX tag or the MODULE_LICENSE, use it as the definitive source of the
licence, and fixup the others when there are contradictions.

Cc: David Wu <david.wu@rock-chips.com>
Cc: Dongpo Li <lidongpo@hisilicon.com>
Cc: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>