kbuild: in makefile.txt note that Makefile is preferred name for kbuild files

As noted by Roland Dreier <rdreier@cisco.com> makefiles.txt told
one to use the name 'Kbuild' as preferred name for kbuild files.
This is not yet true so let makefiles.txt reflect reality.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 99d51a5..a9c00fa 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -106,9 +106,9 @@
 Most Makefiles within the kernel are kbuild Makefiles that use the
 kbuild infrastructure. This chapter introduce the syntax used in the
 kbuild makefiles.
-The preferred name for the kbuild files is 'Kbuild' but 'Makefile' will
-continue to be supported. All new developmen is expected to use the
-Kbuild filename.
+The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can
+be used and if both a 'Makefile' and a 'Kbuild' file exists then the 'Kbuild'
+file will be used.
 
 Section 3.1 "Goal definitions" is a quick intro, further chapters provide
 more details, with real examples.