Provide both mdt and mbn file symlinks

Modern kernels default to .mbn "squashed" blobs instead of .mdt + .bXX

Add a pass on the target dir to add an .mbn symlink for each .mdt, which would allow us to support both old and new kernels. The kernel autodetects the blob type so the file name doesn't matter anyway.

See also: https://lore.kernel.org/linux-arm-msm/2abbae30-f92e-33e4-5509-8979129da665@linaro.org/