cmake: modules: dts: fix in/out docs

The input/output documentation of dts.cmake and pre_dt.cmake was
outdated.

Signed-off-by: Florian Grandel <fgrandel@code-for-humans.de>

cmake/modules/dts.cmake

@@ -66,13 +66,21 @@ find_package(Dtc 1.4.6)
 #
 # Required variables:
 # - BINARY_DIR_INCLUDE_GENERATED: where to put generated include files
+# - DTS_ROOT: a deduplicated list of places where devicetree
+#   implementation files (like bindings, vendor prefixes, etc.) are
+#   found
+# - DTS_ROOT_SYSTEM_INCLUDE_DIRS: set to "PATH1 PATH2 ...",
+#   with one path per potential location where C preprocessor #includes
+#   may be found for devicetree files
 # - KCONFIG_BINARY_DIR: where to put generated Kconfig files
 #
 # Optional variables:
 # - BOARD: board name to use when looking for DTS_SOURCE
 # - BOARD_DIR: board directory to use when looking for DTS_SOURCE
 # - BOARD_REVISION_STRING: used when looking for a board revision's
 #   devicetree overlay file in BOARD_DIR
+# - CMAKE_DTS_PREPROCESSOR: the path to the preprocessor to use
+#   for devicetree files
 # - DTC_OVERLAY_FILE: list of devicetree overlay files which will be
 #   used to modify or extend the base devicetree.
 # - EXTRA_DTC_OVERLAY_FILE: list of extra devicetree overlay files.

cmake/modules/pre_dt.cmake

@@ -11,8 +11,6 @@ include(extensions)
 # Outcome:
 # The following variables will be defined when this CMake module completes:
 #
-# - CMAKE_DTS_PREPROCESSOR: the path to the preprocessor to use
-#   for devicetree files
 # - DTS_ROOT: a deduplicated list of places where devicetree
 #   implementation files (like bindings, vendor prefixes, etc.) are
 #   found