[mips] Use `formatImm` call to print immediate value in the `MipsInstPrinter`

[atanasyan]

Summary

That allows, for example, to print hex-formatted immediates using llvm-objdump --print-imm-hex command line option.

[dsanders]

LGTM

llvm/trunk/lib/Target/Mips/InstPrinter/MipsInstPrinter.cpp

void MipsInstPrinter::printOperand(const MCInst *MI, unsigned OpNo,
                                    raw_ostream &O) {
   const MCOperand &Op = MI->getOperand(OpNo);
   if (Op.isReg()) {
     printRegName(O, Op.getReg());
     return;
   }
 
   if (Op.isImm()) {
-    O << Op.getImm();
+    O << formatImm(Op.getImm());
     return;
   }
 
   assert(Op.isExpr() && "unknown operand kind in printOperand");
   printExpr(Op.getExpr(), &MAI, O);
 }
 
 template <unsigned Bits, unsigned Offset>
 void MipsInstPrinter::printUImm(const MCInst *MI, int opNum, raw_ostream &O) {
   const MCOperand &MO = MI->getOperand(opNum);
   if (MO.isImm()) {
     uint64_t Imm = MO.getImm();
     Imm -= Offset;
     Imm &= (1 << Bits) - 1;
     Imm += Offset;
-    O << Imm;
+    O << formatImm(Imm);
     return;
   }
 
   printOperand(MI, opNum, O);
 }
 
 void MipsInstPrinter::
 printMemOperand(const MCInst *MI, int opNum, raw_ostream &O) {

llvm/trunk/test/MC/Mips/hex-immediates.s

+# RUN: llvm-mc -filetype=obj %s -triple=mips-unknown-linux \
+# RUN:   | llvm-objdump -d --print-imm-hex - | FileCheck %s
+
+# CHECK: jal   0x20
+# CHECK: addiu $sp, $sp, -0x20
+# CHECK: sw    $2,  0x10($fp)
+
+jal     32
+addiu   $sp, $sp, -32
+sw      $2, 16($fp)
+lui     $2, 2