RISC-V: Use a local variable instead of smp_processor_id()

Store the smp_processor_id() in a local variable to save some
pointer chasing.
Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/kernel/smpboot.c

@@ -146,6 +146,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
 asmlinkage __visible void smp_callin(void)
 {
 	struct mm_struct *mm = &init_mm;
+	unsigned int curr_cpuid = smp_processor_id();
 
 	if (!IS_ENABLED(CONFIG_RISCV_SBI))
 		clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
@@ -155,9 +156,9 @@ asmlinkage __visible void smp_callin(void)
 	current->active_mm = mm;
 
 	trap_init();
-	notify_cpu_starting(smp_processor_id());
-	update_siblings_masks(smp_processor_id());
-	set_cpu_online(smp_processor_id(), 1);
+	notify_cpu_starting(curr_cpuid);
+	update_siblings_masks(curr_cpuid);
+	set_cpu_online(curr_cpuid, 1);
 	/*
 	 * Remote TLB flushes are ignored while the CPU is offline, so emit
 	 * a local TLB flush right now just in case.