ARM: dts: stm32: Add alternate pinmux for ethernet0 pins

ARM: dts: stm32: Add alternate pinmux for ethernet0 pins

Add another mux option for ethernet0 pins, this is used on DHCOM when
the ethernet PHY 50 MHz clock is generated by the MCO2 on PG2 pin and
then fed back via PA1 pin.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Christophe Roullier <christophe.roullier@foss.st.com>
Cc: Gabriel Fernandez <gabriel.fernandez@foss.st.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: linux-clk@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Tested-by: Johann Neuhauser <jneuhauser@dh-electronics.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>