libc: don't export unnecessary symbols

Symbols associated with the internal implementation of memcpy
like routines should be private.

Change-Id: I2b1d1f59006395c29d518c153928437b08f93d16
diff --git a/libc/arch-arm/krait/bionic/memcpy.S b/libc/arch-arm/krait/bionic/memcpy.S
index ea040bc..f7277fc 100644
--- a/libc/arch-arm/krait/bionic/memcpy.S
+++ b/libc/arch-arm/krait/bionic/memcpy.S
@@ -67,7 +67,7 @@
 #define MEMCPY_BASE_ALIGNED __memcpy_base_aligned
 #include "memcpy_base.S"
 
-ENTRY(__memcpy_chk_fail)
+ENTRY_PRIVATE(__memcpy_chk_fail)
         .cfi_startproc
         // Preserve lr for backtrace.
         push    {lr}