Add some x86/x86-64 assembler tests.

Also add divq() and divl() to x86-64 assembler and clean up
a test. This is a follow-up to
    https://android-review.googlesource.com/1355865 .

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing -t 082-inline-execute
Bug: 156736938
Change-Id: Iade33a2250cea481249f6b976bc53c86663cb901
diff --git a/compiler/utils/x86_64/assembler_x86_64.h b/compiler/utils/x86_64/assembler_x86_64.h
index 70072d9..64603ee 100644
--- a/compiler/utils/x86_64/assembler_x86_64.h
+++ b/compiler/utils/x86_64/assembler_x86_64.h
@@ -782,6 +782,8 @@
 
   void idivl(CpuRegister reg);
   void idivq(CpuRegister reg);
+  void divl(CpuRegister reg);
+  void divq(CpuRegister reg);
 
   void imull(CpuRegister dst, CpuRegister src);
   void imull(CpuRegister reg, const Immediate& imm);