Add CONFIG_STM32_DAC_LL_OPS support to the common STM32 DAC driver
(stm32_dac_m3m4_v1). This provides low-level ops (llops) and helper
macros (DAC_ENABLE, DAC_WRITE_DRO, DAC_START_DMA, DAC_STOP_DMA,
DAC_DUMP_REGS) matching the existing interface in stm32l4 and stm32h7.
This allows real-time control applications (such as power converters,
inverters, and function generators) to operate the DAC peripheral directly
without char driver VFS overhead.
Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Daniel P. Carvalho <danieloak@gmail.com>
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