ARM: add migrate_pages() system call

The migrate_pages system call has an assigned number on all architectures
except ARM. When it got added initially in commit d80ade7b32 ("ARM:
Fix warning: #warning syscall migrate_pages not implemented"), it was
intentionally left out based on the observation that there are no 32-bit
ARM NUMA systems.

However, there are now arm64 NUMA machines that can in theory run 32-bit
kernels (actually enabling NUMA there would require additional work)
as well as 32-bit user space on 64-bit kernels, so that argument is no
longer very strong.

Assigning the number lets us use the system call on 64-bit kernels as well
as providing a more consistent set of syscalls across architectures.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm/include/asm/unistd.h

@@ -45,7 +45,6 @@
  * Unimplemented (or alternatively implemented) syscalls
  */
 #define __IGNORE_fadvise64_64
-#define __IGNORE_migrate_pages
 
 #ifdef __ARM_EABI__
 /*

arch/arm/tools/syscall.tbl

@@ -414,3 +414,4 @@
 397	common	statx			sys_statx
 398	common	rseq			sys_rseq
 399	common	io_pgetevents		sys_io_pgetevents
+400	common	migrate_pages		sys_migrate_pages

arch/arm64/include/asm/unistd.h

@@ -44,7 +44,7 @@
 #define __ARM_NR_compat_set_tls		(__ARM_NR_COMPAT_BASE + 5)
 #define __ARM_NR_COMPAT_END		(__ARM_NR_COMPAT_BASE + 0x800)
 
-#define __NR_compat_syscalls		400
+#define __NR_compat_syscalls		401
 #endif
 
 #define __ARCH_WANT_SYS_CLONE

arch/arm64/include/asm/unistd32.h

@@ -821,6 +821,8 @@ __SYSCALL(__NR_statx, sys_statx)
 __SYSCALL(__NR_rseq, sys_rseq)
 #define __NR_io_pgetevents 399
 __SYSCALL(__NR_io_pgetevents, compat_sys_io_pgetevents)
+#define __NR_migrate_pages 400
+__SYSCALL(__NR_migrate_pages, compat_sys_migrate_pages)
 
 /*
  * Please add new compat syscalls above this comment and update