tests: drivers: adc: Enable DMA for nucleo_u083rc board for adc_api

Since DMA is supported by the nucleo_u083rc board, it should be enabled
in the board overlay for the ADC adc_api test, similar to the board
nucleo_h743zi.

Signed-off-by: Mohammad Badawi <zephyr@exalt.ps>
Signed-off-by: Sara Touqan <zephyr@exalt.ps>