boards: renesas: Modify the pinsel for adc0 on ek_ra4l1

Currently, we set P002 (AN000) as the default pin selection
for ADC0 on ek_ra4l1. However, after testing the ADC function
with this pin selection, the ADC function does not work
on this pin.

The main reason is P002 is used for the I2C I/O Port Expander
and is connected to a 10kΩ pull-up resistor.

For the solution, we will select the P003 (AN001)
as default pinsel for adc0

Signed-off-by: Khoa Nguyen <khoa.nguyen.xh@renesas.com>