ARM: DTS: stm32: add STM32F429 SoC and its Discovery board support

All these files comes from kernel v4.15-rc1.

Update some header with correct STMicroelectronics Copyright.

Remove the paragraph about writing to the Free Software
Foundation's mailing address as requested by checkpatch.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>