MIPS: Fix a copy & paste error in unistd.h

Commit 5df4c8db (MIPS: Wire up bpf syscall.) break the N32 build
because of a copy & paste error.
Signed-off-by: NHuacai Chen <chenhc@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/8390/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/include/uapi/asm/unistd.h

@@ -1045,7 +1045,7 @@
 #define __NR_seccomp			(__NR_Linux + 316)
 #define __NR_getrandom			(__NR_Linux + 317)
 #define __NR_memfd_create		(__NR_Linux + 318)
-#define __NR_memfd_create		(__NR_Linux + 319)
+#define __NR_bpf			(__NR_Linux + 319)
 
 /*
  * Offset of the last N32 flavoured syscall