[mips] Expose adjustStackPtr() from MipsInstrInfo. NFC.

Summary:
adjustStackPtr() is implemented from both MipsSEInstrInfo and
Mips16InstrInfo. It makes sense to expose this function from
MipsInstrInfo and avoid explicit casting in some cases.

Depends on D8638.

Reviewers: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8640

llvm-svn: 233905
diff --git a/llvm/lib/Target/Mips/MipsInstrInfo.h b/llvm/lib/Target/Mips/MipsInstrInfo.h
index 7b2b289..4589535 100644
--- a/llvm/lib/Target/Mips/MipsInstrInfo.h
+++ b/llvm/lib/Target/Mips/MipsInstrInfo.h
@@ -117,6 +117,10 @@
                                 const TargetRegisterInfo *TRI,
                                 int64_t Offset) const = 0;
 
+  virtual void adjustStackPtr(unsigned SP, int64_t Amount,
+                              MachineBasicBlock &MBB,
+                              MachineBasicBlock::iterator I) const = 0;
+
   /// Create an instruction which has the same operands and memory operands
   /// as MI but has a new opcode.
   MachineInstrBuilder genInstrWithNewOpc(unsigned NewOpc,