Split RelativePatcher::ReserveSpace() into two.

Instead of passing nullptr and MethodReference(nullptr, 0u)
to ReserveSpace() at the end, call a newly created function
ReserveSpaceEnd().

Change-Id: I38815fe9464b4e1a919878b6e8577614f1058d00
diff --git a/compiler/linker/x86/relative_patcher_x86_base.h b/compiler/linker/x86/relative_patcher_x86_base.h
index 1f38cf2..9200709 100644
--- a/compiler/linker/x86/relative_patcher_x86_base.h
+++ b/compiler/linker/x86/relative_patcher_x86_base.h
@@ -27,6 +27,7 @@
   uint32_t ReserveSpace(uint32_t offset,
                         const CompiledMethod* compiled_method,
                         MethodReference method_ref) OVERRIDE;
+  uint32_t ReserveSpaceEnd(uint32_t offset) OVERRIDE;
   uint32_t WriteThunks(OutputStream* out, uint32_t offset) OVERRIDE;
   void PatchCall(std::vector<uint8_t>* code, uint32_t literal_offset,
                  uint32_t patch_offset, uint32_t target_offset) OVERRIDE;