samples: drivers: stm32l562 octospi enables DMA

Adds the dma transfer for the octoSPI on NOR octo Flash
of the stm32l562e_dk disco kit.
The channel for the DMAMUX is 0-15 (0-7 for DMA1, 8-15 for DMA2)
The DMAMUX request is 41 for the OCTOSPI.

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