internal/syscall/unix: apply fstatat fix to linux/mips64le

internal/syscall/unix: apply fstatat fix to linux/mips64le

Apply CL 633280 to linux/mips64le, as it has the same struct as
mips64.

Updates #70659.

Change-Id: Ibab635e69e44682eb214bf6a00f4cd75816b2d34
Reviewed-on: https://go-review.googlesource.com/c/go/+/637739
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>