Kernel prepatch 5.15-rc4

The 5.15-rc4 kernel prepatch is out fortesting.

One thing standing out in the diffs might be the m68k 'set_fs()'removal - not really a regression fix, but it has been pending fora while, and it turned out that the problems attributed to it weredue to an entirely unrelated m68k signal handling issue. So withthat fixed, we could get rid of set_fs from another architecture.

See this article for information onset_fs() and its removal.