[mips] Emit .reloc R_{MICRO}MIPS_JALR along with j(al)r(c) $25

The callee address is added as an optional operand (MCSymbol) in
AdjustInstrPostInstrSelection() and then used by asm printer to insert:
'.reloc tmplabel, R_MIPS_JALR, symbol
tmplabel:'.
Controlled with '-mips-jalr-reloc', default is true.

Differential revision: https://reviews.llvm.org/D56694

llvm-svn: 351485
diff --git a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index d2fed68..f10d100 100644
--- a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -65,10 +65,7 @@
 
 } // end namespace llvm
 
-static cl::opt<bool>
-EmitJalrReloc("mips-jalr-reloc", cl::Hidden,
-              cl::desc("MIPS: Emit R_{MICRO}MIPS_JALR relocation with jalr"),
-              cl::init(true));
+extern cl::opt<bool> EmitJalrReloc;
 
 namespace {