kbuild: rpm-pkg: make sure to have versioned 'Obsoletes' for kernel.spec

Fix the following rpmbuild warning:

  $ make srcrpm-pkg
  ...
  RPM build warnings:
      line 34: It's not recommended to have unversioned Obsoletes: Obsoletes: kernel-headers
Signed-off-by: Rafael Aquini <aquini@redhat.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/package/kernel.spec

@@ -27,7 +27,7 @@ The Linux Kernel, the operating system core itself
 %package headers
 Summary: Header files for the Linux kernel for use by glibc
 Group: Development/System
-Obsoletes: kernel-headers
+Obsoletes: kernel-headers < %{version}
 Provides: kernel-headers = %{version}
 %description headers
 Kernel-headers includes the C header files that specify the interface