arm64: add CPU field to struct thread_info

The CPU field will be moved back into thread_info even when
THREAD_INFO_IN_TASK is enabled, so add it back to arm64's definition of
struct thread_info.

Note that arm64 always has CONFIG_SMP=y so there is no point in guarding
the CPU field with an #ifdef.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>

arch/arm64/include/asm/thread_info.h

@@ -42,6 +42,7 @@ struct thread_info {
 	void			*scs_base;
 	void			*scs_sp;
 #endif
+	u32			cpu;
 };
 
 #define thread_saved_pc(tsk)	\

arch/arm64/kernel/asm-offsets.c

@@ -29,6 +29,7 @@ int main(void)
   DEFINE(TSK_ACTIVE_MM,		offsetof(struct task_struct, active_mm));
   DEFINE(TSK_CPU,		offsetof(struct task_struct, cpu));
   BLANK();
+  DEFINE(TSK_TI_CPU,		offsetof(struct task_struct, thread_info.cpu));
   DEFINE(TSK_TI_FLAGS,		offsetof(struct task_struct, thread_info.flags));
   DEFINE(TSK_TI_PREEMPT,	offsetof(struct task_struct, thread_info.preempt_count));
 #ifdef CONFIG_ARM64_SW_TTBR0_PAN