ARM: dts: stm32: Fix TA3-GPIO-C key on STM32MP1 DHCOM PDK2

On the prototype DHCOM, the TA3-GPIO-C button was connected to pin PI11 of
the STM32MP15xx, however on the production SoM this was changed to pin PG0
to free up the IRQ line 11 for LAN8710i PHY IRQ. Update the connection in
the DT. Since the IRQ line 0 is used for PMIC as well and cannot be shared
with the button, make the button polled.

Fixes: 87cabf94 ("ARM: dts: stm32: Add GPIO keys for STM32MP1 DHCOM PDK2")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>