kernel.bbclass: Remove warnings for modutils and modprobe.d

kernel.bbclass: Remove warnings for modutils and modprobe.d

Fixes [Yocto #2036]

The source and build directories are unused, remove them.

The modutils and modprobe.d directories may be used if modules are built that
are either autoloaded or have modprobe.d entries. This isn't known at install
time, so check after the package split if these directories are empty and
remove them if they are.

(From OE-Core rev: 6068f3229397baf561b1e84a22b570a803d95c49)

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
CC: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>