libm: rename LIBC_PRIVATE to LIBC_DEPRECATED

Bug: http://b/26386014
Change-Id: Ia32411ce779f9dcf2cf7910d8658ffa753c73af9
diff --git a/libm/libm.mips.map b/libm/libm.mips.map
index 476c6ad..2429dba 100644
--- a/libm/libm.mips.map
+++ b/libm/libm.mips.map
@@ -272,7 +272,7 @@
     *;
 };
 
-LIBC_PRIVATE { # arm mips
+LIBC_DEPRECATED { # arm mips
   global: # arm mips
     __fixdfdi; # arm mips
     __fixsfdi; # arm mips