ARM: multi_v7_defconfig: enable STM32 analog & timer drivers

ARM: multi_v7_defconfig: enable STM32 analog & timer drivers

This enables drivers for STM32 timer, low power timer and analog hardware
that can be used on STM32MP1 SoC:
- Timer & LP Timer MFD core, PWM, trigger & encoder drivers
- IIO ADC/DAC/DFSDM
- vrefbuf regu driver (voltage reference buffer).

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Olof Johansson <olof@lixom.net>