tests: drivers: dma adapt the dma tests applications for stm32 devices

It adds flexibility to test different dma channels
The chan_blen_transfer is modified
like the loop_transfer application to support stm32xx devices
with dma and/or dmamux.
On the stm32 devices, the first dma channel is 1.

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