Improve check and definition of radio frequency for TI Simple Link

***NO_CI***

Author: antoniofagundes

Diff for: CMake/binutils.TI_SimpleLink.cmake

@@ -55,12 +55,12 @@ endmacro()
 function(nf_check_radio_frequency)
 
     if(NOT DEFINED RADIO_FREQUENCY)
-        message(FATAL_ERROR "Radio frequncy NOT defined. Please set build option 'RADIO_FREQUENCY'. Valid values are 868 and 915.")
+        message(FATAL_ERROR "\nRadio frequency NOT defined!!\nPlease set the build option 'RADIO_FREQUENCY' in 'config\\user-prefs.json' or in the user CMake preset. Valid values are 868 and 915.\n")
     endif()
 
     # check if file exists
     if(NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/${TARGET_BOARD}_${RADIO_FREQUENCY}.syscfg")
-        message(FATAL_ERROR "Couldn't find a sysconfig file for radio frequency ${RADIO_FREQUENCY}. Valid values are 868 and 915.")
+        message(FATAL_ERROR "\nCouldn't find a sysconfig file for radio frequency ${RADIO_FREQUENCY}.\n")
     endif()
 
 endfunction()

Diff for: config/user-prefs.TEMPLATE.json

@@ -18,7 +18,8 @@
                 "NF_PLATFORM_NO_CLR_TRACE": "OFF",
                 "NF_CLR_NO_IL_INLINE": "OFF",
                 "NF_FEATURE_WATCHDOG": "ON",
-                "SWO_OUTPUT": "OFF"
+                "SWO_OUTPUT": "OFF",
+                "RADIO_FREQUENCY": "CHANGE_ME_TO_A_VALID_VALUE_868_OR_915"
             }
         }
     ],

Diff for: targets/TI_SimpleLink/TI_CC1352R1_LAUNCHXL/CMakePresets.json

@@ -36,8 +36,7 @@
                 "API_nanoFramework.System.Collections": "OFF",
                 "API_nanoFramework.System.Text": "ON",
                 "API_nanoFramework.TI.EasyLink": "ON",
-                "API_nanoFramework.Hardware.TI": "ON",
-                "RADIO_FREQUENCY": "CHANGE_ME_TO_A_VALID_VALUE_868_OR_915"
+                "API_nanoFramework.Hardware.TI": "ON"
             }
         }
     ],