unix: add Fadvise on linux/{arm64,mipsx.mips64x,ppx64x,sparc64}

Change-Id: I3b32b6343e9bc0bb6a205ada9941b4bb9ef91a23
Reviewed-on: https://go-review.googlesource.com/101895
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/syscall_linux_mips64x.go b/unix/syscall_linux_mips64x.go
index 15a69cb..090ed40 100644
--- a/unix/syscall_linux_mips64x.go
+++ b/unix/syscall_linux_mips64x.go
@@ -9,6 +9,7 @@
 
 //sys	Dup2(oldfd int, newfd int) (err error)
 //sys	EpollWait(epfd int, events []EpollEvent, msec int) (n int, err error)
+//sys	Fadvise(fd int, offset int64, length int64, advice int) (err error) = SYS_FADVISE64
 //sys	Fchown(fd int, uid int, gid int) (err error)
 //sys	Fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_NEWFSTATAT
 //sys	Fstatfs(fd int, buf *Statfs_t) (err error)