nobody is probably using 5.15 with newer release and there are issues with "iw reg" since
wireless-regdb upgrade in oe-core as well as shown in:
https://github.com/agherzan/meta-raspberrypi/pull/1317
so better to drop it from master/scarthgap together with
rpi.scc used only for 5.15 and 0001-gcc-plugins-Reorganize-gimple-includes-for-GCC-13.patch
used only by rpi.scc
6.1 version was used by default since mickledore: https://github.com/agherzan/meta-raspberrypi/commit/12a1187b01644cb444106f7c8f498fbf519be276 and kirkstone for rpi5 MACHINEs since: https://github.com/agherzan/meta-raspberrypi/commit/9dc6673d41044f1174551120ce63501421dbcd85
scarthgap uses 6.6 by default since: https://github.com/agherzan/meta-raspberrypi/commit/1cf3dd5e5ef86c5196c8544853857ab1561c748b
nobody is probably using 5.15 with newer release and there are issues with "iw reg" since wireless-regdb upgrade in oe-core as well as shown in: https://github.com/agherzan/meta-raspberrypi/pull/1317 so better to drop it from master/scarthgap together with rpi.scc used only for 5.15 and 0001-gcc-plugins-Reorganize-gimple-includes-for-GCC-13.patch used only by rpi.scc