dt-bindings: Drop DT_MK_SCHEMA_FLAGS conditional selecting schema files

Since commit ef8795f3 ("dt-bindings: kbuild: Use DTB files for
validation"), dt-mk-schema always needs a complete list of schemas, so
the conditional using DT_MK_SCHEMA_FLAGS should be removed.
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220727211100.3249417-1-robh@kernel.org

Documentation/devicetree/bindings/Makefile

@@ -42,9 +42,7 @@ quiet_cmd_chk_bindings = CHKDT   $@
 
 quiet_cmd_mk_schema = SCHEMA  $@
       cmd_mk_schema = f=$$(mktemp) ; \
-                      $(if $(DT_MK_SCHEMA_FLAGS), \
-                           printf '%s\n' $(real-prereqs), \
-                           $(find_all_cmd)) > $$f ; \
+                      $(find_all_cmd) > $$f ; \
                       $(DT_MK_SCHEMA) -j $(DT_MK_SCHEMA_FLAGS) @$$f > $@ ; \
 		      rm -f $$f