tests: drivers: dac loopback on stm32 boards fix pinout

Change the pinout for ADC/DAC loopback testing on the stm32 boards
nucleo_l073rz: adc_in0_pa0/dac_out1_pa4 --> A0 to A2 on arduino CN8
nucleo_g071rb: adc1_in0_pa0/dac1_out1_pa4 --> A0 to A2 on arduino CN8
stm32l562e_dk: adc1_in13_pc4/dac1_out1_pa4 --> A2 to A4 on arduino CN19
Adjust the ACQuisition time to the MAX value because the default (=0)
is too low for several boards.

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