board: stm32f429-disco: switch to DM STM32 pinctrl and gpio driver

Use available DM stm32f7_gpio.c and pinctrl_stm32.c drivers
instead of board GPIO initialization.

Remove stm32_gpio.c which is no more used and migrate
structs stm32_gpio_regs and stm32_gpio_priv into
arch-stm32f4/gpio.h to not break compilation.

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