Hide __signalfd4, used to implement signalfd(3).

Bug: 11156955
Change-Id: I50842279cb5b32ec8bd45193435574e415cd806e
diff --git a/libc/arch-mips/syscalls/signalfd4.S b/libc/arch-mips/syscalls/__signalfd4.S
similarity index 87%
rename from libc/arch-mips/syscalls/signalfd4.S
rename to libc/arch-mips/syscalls/__signalfd4.S
index e2c2a30..cc9b212 100644
--- a/libc/arch-mips/syscalls/signalfd4.S
+++ b/libc/arch-mips/syscalls/__signalfd4.S
@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(signalfd4)
+ENTRY(__signalfd4)
     .set noreorder
     .cpload t9
     li v0, __NR_signalfd4
@@ -16,4 +16,4 @@
     j t9
     nop
     .set reorder
-END(signalfd4)
+END(__signalfd4)