kernel.bbclass: remove default module_autoload and module_conf values

kernel.bbclass: remove default module_autoload and module_conf values

kernel.bbclass is a common class for many different kernel versions,
and as such the default module_autoload and module_conf values that
it contains are not relevant, or out of date for most builds.

Individual kernel recipes or distros can better specify these
values to meet their needs.

(From OE-Core rev: a134efa7743edc3b7ca8abb651add6d2045c3b44)

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