Hide __signalfd4, used to implement signalfd(3).

Bug: 11156955
Change-Id: I50842279cb5b32ec8bd45193435574e415cd806e
diff --git a/libc/arch-mips64/syscalls/signalfd4.S b/libc/arch-mips64/syscalls/__signalfd4.S
similarity index 86%
rename from libc/arch-mips64/syscalls/signalfd4.S
rename to libc/arch-mips64/syscalls/__signalfd4.S
index 594c73d..c4fe77b 100644
--- a/libc/arch-mips64/syscalls/signalfd4.S
+++ b/libc/arch-mips64/syscalls/__signalfd4.S
@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(signalfd4)
+ENTRY(__signalfd4)
     .set push
     .set noreorder
     li v0, __NR_signalfd4
@@ -22,4 +22,5 @@
     j t9
     move ra, t0
     .set pop
-END(signalfd4)
+END(__signalfd4)
+.hidden __signalfd4