patches for stable releases (hexagon related)

Hi,

please consider applying the following patches to v5.10.y and v5.12.y stable branches.

788dcee0306e Hexagon: fix build errors f1f99adf05f2 Hexagon: add target builtins to kernel 6fff7410f6be Hexagon: change jumps to must-extend in futex_atomic_*

The patches are needed to enable hexagon build tests using clang in v5.10.y and v5.12.y.

Thanks, Guenter