Add a series file to order the patches in patches/linux-<version>

Add a series file to order the patches in patches/linux-<version>

The initial ordering is the same as produced by the previous shell
globbing method.

The series file is a simple list of patch files relative to the
patches/linux-<version>/ directory. We do not support comments,
trailing directives (e.g. "-pN") or blank lines. Apart from these
restrictions the series file should be compatible with patch queue
management tools such as quilt.

Signed-off-by: Ian Campbell <ian.campbell@xensource.com>