kbuild: deb-pkg: specify targets in debian/rules as .PHONY

If a file with the same name exists, the target is not run.

For example, the following command fails.

  $ make O=build-arch bindeb-pkg
    [ snip ]
  sed: can't read modules.order: No such file or directory
  make[6]: *** [../Makefile:1577: __modinst_pre] Error 2
  make[5]: *** [../scripts/Makefile.package:150: intdeb-pkg] Error 2
  make[4]: *** [../Makefile:1657: intdeb-pkg] Error 2
  make[3]: *** [debian/rules:14: binary-arch] Error 2
  dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2
  make[2]: *** [../scripts/Makefile.package:139: bindeb-pkg] Error 2

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>