ARM: dts: Add USART1 pin config to STM32F429 boards

This patch selects USART1 pin configuration on PA9/PA10 pins
for both Eval and Disco boards.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>