tests: adc: cleanup test tags

Remove platform specific tags and be consistent.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

samples/boards/stm32/power_mgmt/adc/sample.yaml

@@ -3,7 +3,7 @@ sample:
 tests:
   sample.boards.stm32.power_mgmt.adc:
     tags:
-      - ADC
+      - adc
       - power
     harness: console
     harness_config:

samples/drivers/adc/sample.yaml

@@ -2,7 +2,8 @@ sample:
   name: ADC driver sample
 tests:
   sample.drivers.adc:
-    tags: ADC
+    tags:
+      - adc
     depends_on: adc
     platform_allow:
       - nucleo_l073rz

samples/drivers/soc_flash_nrf/sample.yaml

@@ -10,8 +10,7 @@ tests:
       - nrf52dk_nrf52832
     tags:
       - flash
-      - nrf52
+      - drivers
-      - nrf9160
     harness: console
     harness_config:
       fixture: external_flash

tests/drivers/build_all/adc/testcase.yaml

@@ -9,53 +9,30 @@ tests:
     platform_allow:
       - native_posix
       - native_posix_64
-    tags:
-      - adc_mcp302x
-      - adc_lmp90xxx
-      - adc_ads1x1x
-      - adc_ads1119
-      - adc_ads1112
-      - adc_ads114s08
-      - adc_emul
-      - adc_max1125x
-      - adc_ltc2451
     extra_args: "CONFIG_GPIO=y"
   drivers.adc.cc32xx.build:
     platform_allow: cc3220sf_launchxl
-    tags: adc_cc32xx
   drivers.adc.ite.it8xxx2.build:
     platform_allow: it8xxx2_evb
-    tags: adc_ite_it8xxx2
   drivers.adc.mcux.adc12.build:
     platform_allow: twr_ke18f
-    tags: adc_mcux_adc12
   drivers.adc.mcux.adc16.build:
     platform_allow: frdm_k22f
-    tags: adc_mcux_adc16
   drivers.adc.mcux.lpadc.build:
     platform_allow: lpcxpresso55s28
-    tags: adc_mcux_lpadc
   drivers.adc.npcx.build:
     platform_allow: npcx7m6fb_evb
-    tags: adc_npcx
   drivers.adc.nrf.build:
     platform_allow: nrf51dk_nrf51422
-    tags: adc_nrfx_adc
   drivers.adc.nrf.saadc.build:
     platform_allow: nrf21540dk_nrf52840
-    tags: adc_nrfx_saadc
   drivers.adc.sam0.build:
     platform_allow: atsame54_xpro
-    tags: adc_sam0
   drivers.adc.sam.afec.build:
     platform_allow: sam_e70_xplained
-    tags: adc_sam_afec
   drivers.adc.stm32.build:
     platform_allow: disco_l475_iot1
-    tags: adc_stm32
   drivers.adc.xec.build:
     platform_allow: mec15xxevb_assy6853
-    tags: adc_xec
   drivers.adc.test.build:
     platform_allow: qemu_cortex_m3
-    tags: adc_test