This is a problem introduced by a distribution update.
It builds fine for distributions which use a version of patch <= 2.6.1. All distributions listed on the sanity tested distros in sources/meta-digi/meta-digi-dey/conf/distro/dey.conf should work, assuming they have not been upgraded afterwards.
That's why the problem has not been detected by Digi build servers which run on Ubuntu 12.04, which was the reference distribution at the time of the dey-1.4 release.
Versions of patch > 2.6.1 introduced a check for patches which include git binary files. It applies them correctly ignoring the binary files but returns an exit status of 1 which causes yocto to set the patch operation as failed.
I enclose a reworked patch for 0001-gst-fsl-plugin-update-to-DEL-revision.patch
 removing the deletion of a binary file. This was an unused tgz file which was removed as part of a cleanup.
Although I don't expect issues with the enclosed patch, I would recommend to use a supported distribution or wait for a new hotfix release.
Please report any problems in using the patch.