Fix the values of two xcore ELF flags.

The values in llvm grew from a pre-MC day when they would not show up
in .o files and are outside of the SHF_MASKPROC.

Fortunately the MC output is not currently used as xcore has its own
assemble and that assembler uses valid values. This updates llvm to
use the same values as the xmos assembler.

llvm-svn: 293480