system/core: rename aarch64 target to arm64

Rename aarch64 build targets to arm64.  The gcc toolchain is still
aarch64.

Change-Id: Ia92d8a50824e5329cf00fd6f4f92eae112b7f3a3
diff --git a/libpixelflinger/codeflinger/GGLAssembler.cpp b/libpixelflinger/codeflinger/GGLAssembler.cpp
index 7f088db..2422d7b 100644
--- a/libpixelflinger/codeflinger/GGLAssembler.cpp
+++ b/libpixelflinger/codeflinger/GGLAssembler.cpp
@@ -901,7 +901,7 @@
         AND( AL, 0, d, s, imm(mask) );
         return;
     }
-    else if (getCodegenArch() == CODEGEN_ARCH_AARCH64) {
+    else if (getCodegenArch() == CODEGEN_ARCH_ARM64) {
         AND( AL, 0, d, s, imm(mask) );
         return;
     }