modules: introduces module_kconfig directive

modules: introduces module_kconfig directive

module_kconfig is a new directive that should be used with module_obj
whenever that module depends on the Kconfig to be enabled.

When the module is enabled in Kconfig we are sure that its dependencies
will be enabled as well, thus the module will be loaded without any
problem.

The correct way to use module_kconfig is by passing the Kconfig option
to module_kconfig (or the *config-devices.mak without CONFIG_).

Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
Message-Id: <165369002370.5857.12150544416563557322.stgit@work>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>