[Sparc] Implement BFD_RELOC_NONE

`instrprof-icall-promo.test` `FAIL`s on Solaris/sparcv9:

  Profile-sparc :: instrprof-icall-promo.test
  Profile-sparcv9 :: instrprof-icall-promo.test

when compiling `compiler-rt/test/profile/Inputs/instrprof-icall-promo_2.cpp` with

  fatal error: error in backend: Relocation for CG Profile could not be created: unknown relocation name

This happens because the Sparc backend doesn't implement `BFD_RELOC_NONE`.
This patch fixes that, following what X86 does.

Tested on `sparcv9-sun-solaris2.11`.

Differential Revision: https://reviews.llvm.org/D118136