[llvm-branch-commits] [NFCI][ELF][Mips] Replace MipsMultiGotPage with new RE_MIPS_OSEC_LOCAL_PAGE (PR #150810)

[Jessica Clarke via llvm-branch-commits]

https://github.com/jrtc27 created https://github.com/llvm/llvm-project/pull/150810

Instead of having a special DynamicReloc::Kind, we can just use a new
RelExpr for the calculation needed. The only odd thing we do that allows
this is to keep a representative symbol for the OutputSection in
question (the first we see for it) around to use in this relocation for
the addend calculation.

This reduces DynamicReloc to just AddendOnly vs AgainstSymbol, plus the
internal Computed.