samples: drivers: adc: naming adc sample

The adc sample was in the root directory of the adc samples.
Move all the files to a subdirectory adc_dt.

Signed-off-by: Paulo Santos <pauloroberto.santos@edge.ufal.br>

samples/drivers/adc/adc_dt/sample.yaml

@@ -0,0 +1,41 @@
+sample:
+  name: ADC devicetree driver sample
+tests:
+  sample.drivers.adc.adc_dt:
+    tags:
+      - adc
+    depends_on: adc
+    platform_allow:
+      - nucleo_l073rz
+      - disco_l475_iot1
+      - cc3220sf_launchxl
+      - cc3235sf_launchxl
+      - cy8cproto_063_ble
+      - stm32l496g_disco
+      - stm32h735g_disco
+      - nrf51dk/nrf51822
+      - nrf52840dk/nrf52840
+      - mec172xevb_assy6906
+      - gd32f350r_eval
+      - gd32f450i_eval
+      - gd32vf103v_eval
+      - gd32f403z_eval
+      - esp32_devkitc_wroom/esp32/procpu
+      - esp32_devkitc_wrover/esp32/procpu
+      - esp32s2_saola
+      - esp32c3_devkitm
+      - gd32l233r_eval
+      - lpcxpresso55s36
+      - mr_canhubk3
+      - longan_nano
+      - longan_nano/gd32vf103/lite
+    integration_platforms:
+      - nucleo_l073rz
+      - nrf52840dk/nrf52840
+    harness: console
+    timeout: 10
+    harness_config:
+      type: multi_line
+      regex:
+        - "ADC reading\\[\\d+\\]:"
+        - "- .+, channel \\d+: -?\\d+"