tests: drivers: adc: api: add test for nucleo_f103rb with dma

Adds an ADC DMA test for Nucleo F103RB board now that support for it is
added in the ADC driver.
Reading multiple channels in F1 is only possible with the DMA, hence the
necessity to have a dedicated twister test for it.

Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>