dm: reset: add stm32 reset driver

This driver is adapted from linux drivers/reset/reset-stm32.c
It's compatible with STM32 F4/F7/H7 SoCs.

This driver doesn't implement .of_match as it's binded
by MFD RCC driver.

To add support for each SoC family, a SoC's specific
include/dt-binfings/mfd/stm32xx-rcc.h file must be added.

This patch only includes stm32h7-rcc.h dedicated for STM32H7 SoCs.
Other SoCs support will be added in the future.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>