tests: drivers: spi: spi_loopback: stm32: fix dma DTS phandle lists

Correct STM32 boards DTS overlay files DMA lists that were not split
by phandle and seemed to form unique phandles. This is not currently
an issue with existing DT parsing macros and tools but may generate
build errors if tools are more strict on the DTS implementation format.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
28 files changed