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-*

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
package_rpm.bbclass: Optimise per file dependency handling

Currently the process for injecting the per file rpm dependencies into
rpmbuild is painfully slow. Its done through the repeated execution of
a script which has to return the correct value in each case. This continual
execution means the CPU usage of rpmbuild is low.

This patch allows the option of collapsing the per file dependencies to
a per package basis and injecting them through the .spec file. This removes
the execution overhead and allows rpmbuild to run at 100% of cpu.

Ultimately it would be nice to inject the per file dependencies through
the .spec file however that is not currently possible.

Since few people use the per file dependency information, this patch
goes for the faster approach. It can be enabled if anyone needs it although
I'd mention that its being used to us as this code may well go away in
the future if nobody complains.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>