dmaengine: stm32-dma3: introduce channel semaphore helpers

dmaengine: stm32-dma3: introduce channel semaphore helpers

Before restoring semaphore status after suspend, introduce new functions
to handle semaphore operations :
- stm32_dma3_get_chan_sem() to take the semaphore
- stm32_dma3_put_chan_sem() to release the semaphore
Also, use a new boolean variable semaphore_taken, which is true when the
semaphore has been taken and false when it has been released.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://patch.msgid.link/20251121-dma3_improv-v2-2-76a207b13ea6@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>