musl: loongarch64: Fix the struct ipc_perm bindings

Refer: https://git.musl-libc.org/cgit/musl/tree/arch/generic/bits/ipc.h?h=v1.2.5
(cherry picked from commit 65a7737)
(backport <rust-lang#4384>)

Author: heiher

src/unix/linux_like/linux/musl/b64/loongarch64/mod.rs

@@ -65,7 +65,6 @@ s! {
         pub cgid: crate::gid_t,
         pub mode: c_uint,
         pub __seq: c_int,
-        __pad2: c_ushort,
         __unused1: c_ulong,
         __unused2: c_ulong,
     }