ART: Simplify cache flush calls

Remove need to cast to char* for Flush{Data,Instruction}Cache.

Test: Treehugger
Change-Id: I880c327d59624a04bc2a44a741bc40756a0fd3eb
diff --git a/compiler/common_compiler_test.cc b/compiler/common_compiler_test.cc
index d603d96..586891a 100644
--- a/compiler/common_compiler_test.cc
+++ b/compiler/common_compiler_test.cc
@@ -108,7 +108,7 @@
   int result = mprotect(reinterpret_cast<void*>(base), len, PROT_READ | PROT_WRITE | PROT_EXEC);
   CHECK_EQ(result, 0);
 
-  FlushInstructionCache(reinterpret_cast<char*>(base), reinterpret_cast<char*>(base + len));
+  FlushInstructionCache(reinterpret_cast<void*>(base), reinterpret_cast<void*>(base + len));
 }
 
 void CommonCompilerTest::MakeExecutable(ObjPtr<mirror::ClassLoader> class_loader,