Add OpEndIT() for marking the end of OpIT blocks

In ARM we need to prevent code motion to the inside of an
IT block.  This was done using a GenBarrier() to mark the end, but
it wasn't obvious that this is what was happening.  This CL adds
an explicit OpEndIT() that takes the LIR of the OpIT for future
checks.

Bug: 13751744
Change-Id: If41d2adea1f43f11ebb3b72906bd308252ce3d01
diff --git a/compiler/dex/quick/arm/fp_arm.cc b/compiler/dex/quick/arm/fp_arm.cc
index 07a13ce..d72f596 100644
--- a/compiler/dex/quick/arm/fp_arm.cc
+++ b/compiler/dex/quick/arm/fp_arm.cc
@@ -314,14 +314,14 @@
   DCHECK(!ARM_FPREG(rl_result.reg.GetReg()));
   NewLIR0(kThumb2Fmstat);
 
-  OpIT((default_result == -1) ? kCondGt : kCondMi, "");
+  LIR* it = OpIT((default_result == -1) ? kCondGt : kCondMi, "");
   NewLIR2(kThumb2MovI8M, rl_result.reg.GetReg(),
           ModifiedImmediate(-default_result));  // Must not alter ccodes
-  GenBarrier();
+  OpEndIT(it);
 
-  OpIT(kCondEq, "");
+  it = OpIT(kCondEq, "");
   LoadConstant(rl_result.reg, 0);
-  GenBarrier();
+  OpEndIT(it);
 
   StoreValue(rl_dest, rl_result);
 }