arm64: add seccomp syscall for compat task

This patch allows compat task to issue seccomp() system call.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/unistd32.h

@@ -787,7 +787,8 @@ __SYSCALL(__NR_sched_setattr, sys_sched_setattr)
 __SYSCALL(__NR_sched_getattr, sys_sched_getattr)
 #define __NR_renameat2 382
 __SYSCALL(__NR_renameat2, sys_renameat2)
-			/* 383 for seccomp */
+#define __NR_seccomp 383
+__SYSCALL(__NR_seccomp, sys_seccomp)
 #define __NR_getrandom 384
 __SYSCALL(__NR_getrandom, sys_getrandom)
 #define __NR_memfd_create 385