net/memif: set memfd syscall ID for LoongArch

Define the missing __NR_memfd_create syscall id to enable the memif
PMD on LoongArch.

Signed-off-by: Min Zhou <zhoumin@loongson.cn>

drivers/net/memif/meson.build

@@ -1,12 +1,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright 2018-2019 Cisco Systems, Inc.  All rights reserved.
 
-if arch_subdir == 'loongarch'
-    build = false
-    reason = 'not supported on LoongArch'
-    subdir_done()
-endif
-
 if not is_linux
     build = false
     reason = 'only supported on Linux'

drivers/net/memif/rte_eth_memif.h

@@ -182,6 +182,8 @@ const char *memif_version(void);
 #define __NR_memfd_create 356
 #elif defined __riscv
 #define __NR_memfd_create 279
+#elif defined __loongarch__
+#define __NR_memfd_create 279
 #else
 #error "__NR_memfd_create unknown for this architecture"
 #endif