Move to arm-optimized-routines memset().

This one's a bit simpler, because there is only one upstream memset()
implementation.

Test: treehugger
Change-Id: I2536d0eb72adaacfa6a0e40d2bd29fc833988c16
diff --git a/libc/Android.bp b/libc/Android.bp
index 53fd78e..82fc0bc 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -811,8 +811,8 @@
         arm64: {
             cflags: ["-DHAVE_ASSEMBLER___MEMCPY_CHK"],
             srcs: [
-                "arch-arm64/generic/bionic/__memcpy_chk.S",
-                "arch-arm64/generic/bionic/__memset_chk.S",
+                "arch-arm64/string/__memcpy_chk.S",
+                "arch-arm64/string/__memset_chk.S",
             ],
         },
     },
@@ -896,8 +896,6 @@
         },
         arm64: {
             srcs: [
-                "arch-arm64/generic/bionic/memset.S",
-
                 "arch-arm64/bionic/__bionic_clone.S",
                 "arch-arm64/bionic/_exit_with_stack_teardown.S",
                 "arch-arm64/bionic/setjmp.S",
@@ -905,7 +903,6 @@
                 "arch-arm64/bionic/vfork.S",
             ],
             exclude_srcs: [
-                "bionic/__memcpy_chk.cpp",
                 "bionic/strchr.cpp",
                 "bionic/strchrnul.cpp",
                 "bionic/strnlen.c",