dts/arm: STM32: Adding DAC1 & DAC2 support for stm32f3 in dtsi

This commit adds DAC1 support in dtsi for stm32f3 series. Some
stm32f3 series has DAC2 so adding the same where applicable.

Signed-off-by: Krishna Mohan Dani <krishnamohan.d@hcl.com>