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_base.S b/libc/arch-arm/krait/bionic/memcpy_base.S
index d87a542..cc1ab60 100644
--- a/libc/arch-arm/krait/bionic/memcpy_base.S
+++ b/libc/arch-arm/krait/bionic/memcpy_base.S
@@ -35,7 +35,7 @@
 
 // Assumes neon instructions and a cache line size of 32 bytes.
 
-ENTRY(MEMCPY_BASE)
+ENTRY_PRIVATE(MEMCPY_BASE)
         .cfi_startproc
         .save {r0, lr}
         .cfi_def_cfa_offset 8