ARM: dts: stm32: Deduplicate serial aliases and chosen node for STM32MP15xx DHCOM SoM

[ Upstream commit 73317d32 ]

Deduplicate /aliases { serialN = ... } and /chosen node into
stm32mp15xx-dhcom-som.dtsi , since the content is identical
on all carrier boards using the STM32MP15xx DHCOM SoM. No
functional change.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
Stable-dep-of: 479b8227 ("ARM: dts: stm32: Swap USART3 and UART8 alias on STM32MP15xx DHCOM SoM")
Signed-off-by: Sasha Levin <sashal@kernel.org>