recipes: Remove u-boot patches

Patches from layers were applied directly to source code to be able to build the image/u-boot binary after using 'devtool modify u-boot-seco-mtk' and commit changes directly to source code and not create patch files. Otherwise, you need to keep the 'devtool' branch with applied patches and separately commit to a feature-branch because by default patches aren't applied to u-boot source code during the bitbake build if you checked it out with devtool.

Does it make sense to you? Needs to be merged prior to seco-ne/3rd-party/u-boot/u-boot-mtk!4 (merged)