Hide __get_sp.

Bug: 11156955
Change-Id: I55d8d320521e80c2085af28933a18b00cf5c714e
diff --git a/libc/arch-arm/bionic/__get_sp.S b/libc/arch-arm/bionic/__get_sp.S
index aabec6d..9ae6f24 100644
--- a/libc/arch-arm/bionic/__get_sp.S
+++ b/libc/arch-arm/bionic/__get_sp.S
@@ -28,7 +28,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(__get_sp)
+ENTRY_PRIVATE(__get_sp)
   mov r0, sp
   bx lr
 END(__get_sp)