drivers: dma: stm32u5 dma drivers has a suspend function

Gives the stm32u5 dma driver a suspend function to
enhance the dma API.
This is a particular feature of the stm32U5 GPDMA
to suspend a channel.
A delay is required  ;1ms is compatible with both stm32u5 platforms.

Signed-off-by: Francois Ramu <francois.ramu@st.com>