kmod: merge target/native recipes

kmod: merge target/native recipes

There's no good reason to keep separate target and native recipes for
kmod, so merge them into a single kmod_29.bb which uses class extension.

The symlinks are not created differently for target vs native builds, as
the native sbindir is in PATH.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>