kernel-yocto: add bbclass from poky 8f36e1ef

Signed-off-by: Christopher Larson <kergoth@gmail.com>
kernel-yocto: fix beagleboard build breakage

The bbclass did the following:

    do_diffconfig[depends] += "virtual/kernel:do_kernel_configme"

This clearly introduces a cross-kernel task dependency if the recipe
inheriting this class isn't the preferred provider of virtual/kernel, which is
obviously wrong, but further, will break the build if a kernel-yocto based
kernel is parsed and not skipped, but virtual/kernel refers to
a non-kernel-yocto recipe, which would not have the do_kernel_configme task.

Work around this by adding the in-recipe task dep programmatically with
bb.build.addtask conditionally on do_diffconfig's existance.

Signed-off-by: Christopher Larson <kergoth@gmail.com>
mel: BBMASK: mesa 9.2.5 -> %

Upstream switched this to use a wildcard.

Signed-off-by: Christopher Larson <kergoth@gmail.com>