riscv: rely on core code to keep thread_info::cpu updated

Now that the core code switched back to using thread_info::cpu to keep
a task's CPU number, we no longer need to keep it in sync explicitly. So
just drop the code that does this.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>

arch/riscv/kernel/asm-offsets.c

@@ -33,7 +33,6 @@ void asm_offsets(void)
 	OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count);
 	OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp);
 	OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp);
-	OFFSET(TASK_TI_CPU, task_struct, thread_info.cpu);
 
 	OFFSET(TASK_THREAD_F0,  task_struct, thread.fstate.f[0]);
 	OFFSET(TASK_THREAD_F1,  task_struct, thread.fstate.f[1]);

arch/riscv/kernel/entry.S

@@ -544,11 +544,6 @@ ENTRY(__switch_to)
 	REG_L s9,  TASK_THREAD_S9_RA(a4)
 	REG_L s10, TASK_THREAD_S10_RA(a4)
 	REG_L s11, TASK_THREAD_S11_RA(a4)
-	/* Swap the CPU entry around. */
-	lw a3, TASK_TI_CPU(a0)
-	lw a4, TASK_TI_CPU(a1)
-	sw a3, TASK_TI_CPU(a1)
-	sw a4, TASK_TI_CPU(a0)
 	/* The offset of thread_info in task_struct is zero. */
 	move tp, a1
 	ret

arch/riscv/kernel/head.S

@@ -317,7 +317,6 @@ clear_bss_done:
 	call setup_trap_vector
 	/* Restore C environment */
 	la tp, init_task
-	sw zero, TASK_TI_CPU(tp)
 	la sp, init_thread_union + THREAD_SIZE
 
 #ifdef CONFIG_KASAN