Fixes for comparisons between signed and unsigned values with new jb-mr2 compiler

Change-Id: Ibfcf8dca0b36b29548231c829be3c160c1c6d747
diff --git a/src/oat/runtime/arm/context_arm.cc b/src/oat/runtime/arm/context_arm.cc
index 7b45bc2a7..4e42e94 100644
--- a/src/oat/runtime/arm/context_arm.cc
+++ b/src/oat/runtime/arm/context_arm.cc
@@ -70,7 +70,7 @@
 }
 
 void ArmContext::SetGPR(uint32_t reg, uintptr_t value) {
-  DCHECK_LT(reg, kNumberOfCoreRegisters);
+  DCHECK_LT(reg, static_cast<uint32_t>(kNumberOfCoreRegisters));
   DCHECK_NE(gprs_[reg], &gZero); // Can't overwrite this static value since they are never reset.
   DCHECK(gprs_[reg] != NULL);
   *gprs_[reg] = value;