[Support/ELF] - Add OpenBSD PT_OPENBSD_BOOTDATA constant.

OpenBSD commit for reference:
https://github.com/openbsd/src/commit/d39116912b9536bd77326260dc5c6e593fd4ee24

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288816 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed