Revert "Add MIPS64r6 support for libpixelflinger"

This reverts commit ab5265ebe65eac3b9555eaa3f425cf8e2759d3b3.

This broke the mips64 build (which, stupidly, I hadn't tested):

  system/core/libpixelflinger/codeflinger/MIPS64Assembler.h:24:35: fatal error: tinyutils/KeyedVector.h: No such file or directory
   #include "tinyutils/KeyedVector.h"

Change-Id: I4fa1c04e196592fd1ef893a83c75261a55d32290
diff --git a/libpixelflinger/codeflinger/ARMAssemblerInterface.h b/libpixelflinger/codeflinger/ARMAssemblerInterface.h
index 72935ac..40cbfcf 100644
--- a/libpixelflinger/codeflinger/ARMAssemblerInterface.h
+++ b/libpixelflinger/codeflinger/ARMAssemblerInterface.h
@@ -63,7 +63,7 @@
     };
 
     enum {
-        CODEGEN_ARCH_ARM = 1, CODEGEN_ARCH_MIPS, CODEGEN_ARCH_ARM64, CODEGEN_ARCH_MIPS64
+        CODEGEN_ARCH_ARM = 1, CODEGEN_ARCH_MIPS, CODEGEN_ARCH_ARM64
     };
 
     // -----------------------------------------------------------------------
@@ -115,8 +115,7 @@
     // data processing...
     enum {
         opAND, opEOR, opSUB, opRSB, opADD, opADC, opSBC, opRSC, 
-        opTST, opTEQ, opCMP, opCMN, opORR, opMOV, opBIC, opMVN,
-        opADD64, opSUB64
+        opTST, opTEQ, opCMP, opCMN, opORR, opMOV, opBIC, opMVN
     };
 
     virtual void