cmake: Remove support for deprecated prj_board.conf

Removes support for the deprecated features of having a prj file
which has the board name on the end of it. Board Kconfig fragments
should be used instead.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

cmake/modules/FindDeprecated.cmake

@@ -107,13 +107,6 @@ if("SOURCES" IN_LIST Deprecated_FIND_COMPONENTS)
   endif()
 endif()
 
-if("PRJ_BOARD" IN_LIST Deprecated_FIND_COMPONENTS)
-  # This code was deprecated after Zephyr v3.3.0
-  list(REMOVE_ITEM Deprecated_FIND_COMPONENTS PRJ_BOARD)
-  message(DEPRECATION "'prj_<board>.conf' files are deprecated and should be "
-                      "replaced with board Kconfig fragments instead.")
-endif()
-
 if("PYTHON_PREFER" IN_LIST Deprecated_FIND_COMPONENTS)
   # This code was deprecated after Zephyr v3.4.0
   list(REMOVE_ITEM Deprecated_FIND_COMPONENTS PYTHON_PREFER)

cmake/modules/configuration_files.cmake

@@ -68,9 +68,6 @@ elseif(CACHED_CONF_FILE)
   # That value has precedence over anything else than a new
   # `cmake -DCONF_FILE=<file>` invocation.
   set(CONF_FILE ${CACHED_CONF_FILE})
-elseif(EXISTS   ${APPLICATION_CONFIG_DIR}/prj_${BOARD}.conf)
-  set(CONF_FILE ${APPLICATION_CONFIG_DIR}/prj_${BOARD}.conf)
-  find_package(Deprecated COMPONENTS PRJ_BOARD)
 elseif(EXISTS   ${APPLICATION_CONFIG_DIR}/prj.conf)
   set(CONF_FILE ${APPLICATION_CONFIG_DIR}/prj.conf)
   set(CONF_FILE_INCLUDE_FRAGMENTS true)