ART: Fix MIPS build

Wrong name for an assembly file. Also, registers need $ prefix
in our assembler.

Change-Id: Ic2d5961ec7d0c8e65ca5b27d681487da847c9065
diff --git a/runtime/Android.mk b/runtime/Android.mk
index 52b5f43..8f8eeba 100644
--- a/runtime/Android.mk
+++ b/runtime/Android.mk
@@ -256,7 +256,7 @@
 	arch/mips/context_mips.cc \
 	arch/mips/entrypoints_init_mips.cc \
 	arch/mips/jni_entrypoints_mips.S \
-	arch/mips/memcmp16.S \
+	arch/mips/memcmp16_mips.S \
 	arch/mips/portable_entrypoints_mips.S \
 	arch/mips/quick_entrypoints_mips.S \
 	arch/mips/thread_mips.cc \