tests: drivers: spi: spi_loopback: update spi_loopback test

- add nucleo_c071rb overlay file to setup spi and dma nodes

- Add the nucleo_c071rb configuration file to reduce the size of
SPI_LARGE_BUFFER_SIZE to avoid RAM overflow and be able
to run the test.

- update testcase.yaml for CI integration

Signed-off-by: Fabrice DJIATSA <fabrice.djiatsa-ext@st.com>