Move trampolines to thumb2 instead of ARM

Currently the entrypoint trampolines are compiled using the ARM32 assembler.
This changes that to use the thumb2 assembler for consistency with the
other compiled code.

Bug: 15455279
Change-Id: I6bacdf359e2ae4c0967fb5cd9dc694af11f802ec
diff --git a/compiler/compiled_method.cc b/compiler/compiled_method.cc
index 7441dac..f098a34 100644
--- a/compiler/compiled_method.cc
+++ b/compiler/compiled_method.cc
@@ -86,7 +86,11 @@
 }
 
 size_t CompiledCode::CodeDelta() const {
-  switch (instruction_set_) {
+  return CodeDelta(instruction_set_);
+}
+
+size_t CompiledCode::CodeDelta(InstructionSet instruction_set) {
+  switch (instruction_set) {
     case kArm:
     case kArm64:
     case kMips:
@@ -98,7 +102,7 @@
       return 1;
     }
     default:
-      LOG(FATAL) << "Unknown InstructionSet: " << instruction_set_;
+      LOG(FATAL) << "Unknown InstructionSet: " << instruction_set;
       return 0;
   }
 }