libc: Remove duplicate eventfd declaration from SYSCALLS.TXT

The second declaration came from an incorrect change in AOSP.
The eventfd stubs are not affected by this, they are already correct.

Change-Id: Icfc7612a68fc37a48dde2687137960a5d1dbc534
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 2bb8a42..3023b13 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -267,5 +267,3 @@
 # ARM-specific ARM_NR_BASE == 0x0f0000 == 983040
 int     __set_tls:ARM_set_tls(void*)                                 983045,-1
 int     cacheflush:ARM_cacheflush(long start, long end, long flags)  983042,-1
-
-int     eventfd(int count, int flags) 351,323