kbuild: Revert part of e8d400a9 to resolve a conflict

A more complete patch in the kernel-doc tree also contains this change.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Documentation/kbuild/makefiles.txt

@@ -320,7 +320,7 @@ more details, with real examples.
     subdir-ccflags-y, subdir-asflags-y
 	The two flags listed above are similar to ccflags-y and as-falgs-y.
 	The difference is that the subdir- variants has effect for the kbuild
-	file where they are present and all subdirectories.
+	file where tey are present and all subdirectories.
 	Options specified using subdir-* are added to the commandline before
 	the options specified using the non-subdir variants.