ARM: dts: stm32: Fix DH PDK2 display PWM channel

ARM: dts: stm32: Fix DH PDK2 display PWM channel

[ Upstream commit 57592d2a98dbc3bde3ddc062e91a8486bdcb211e ]

The display PWM channel is number 3 (PWM2 CH4), make it so.

Fixes: 34e0c7847dcf ("ARM: dts: stm32: Add DH Electronics DHCOM STM32MP1 SoM and PDK2 board")
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>