drivers/dma: stm32 dmamux: use util_listify to gen. func/dma_chan arrays

This commit continues simplifying the generation of
isActiveFlag/clearFlag funtion pointer array for the request generators
and does the same for the table_ll_channel.
Additionally move struct dmamux_stm32_channel to c file.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>