kernel: extract functions for kernel modules to separate bbclass

kernel: extract functions for kernel modules to separate bbclass

* this way we can reuse the same functionality also for external modules
  including module_autoload_foo and module_conf_foo functionality
* MODULE_PACKAGES variable was removed (splited modules are now returned
  by do_split_packages
* KERNEL_MODULES_META_PACKAGE is used to append all splitted packages
  to RDEPENDS. In kernel.bbclass it's old "kernel-modules" in
  module.bbclass it defaults to ${PN} for upgrade path from
  single PN with all modules to PN depending on all new kernel-module-*

(From OE-Core rev: 51928b6b5ca0a46a9dcd754483a19af58b95fa18)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>