linux-yocto: streamline support for multiple upstream repo types

linux-yocto: streamline support for multiple upstream repo types

In order to support repositories of various types (with or without
meta data, branched, pristine, custom, etc) information about the
type of processing that is required was passed to the processing
phases via variables.

The combination of variables involved in coordinating the processing
creates a learning curve and overly complicates recipe extensions.

With minor tweaks to the kern-tools, adding flexibility and keying
off the existence of the meta branch it is possible to remove all
of the variables that were added to support different repository
types.

(From OE-Core rev: 06e5f45c8f38925cd5902a3a3f436f5e9451dd16)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>