firmware: psci: Replace cpu_up/down() with add/remove_cpu()

The core device API performs extra housekeeping bits that are missing
from directly calling cpu_up/down().

See commit a6717c0 ("powerpc/rtas: use device model APIs and
serialization during LPM") for an example description of what might go
wrong.

This also prepares to make cpu_up/down a private interface of the CPU subsystem.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Link: https://lkml.kernel.org/r/20200323135110.30522-15-qais.yousef@arm.com

drivers/firmware/psci/psci_checker.c

@@ -84,7 +84,7 @@ static unsigned int down_and_up_cpus(const struct cpumask *cpus,
 
 	/* Try to power down all CPUs in the mask. */
 	for_each_cpu(cpu, cpus) {
-		int ret = cpu_down(cpu);
+		int ret = remove_cpu(cpu);
 
 		/*
 		 * cpu_down() checks the number of online CPUs before the TOS
@@ -116,7 +116,7 @@ static unsigned int down_and_up_cpus(const struct cpumask *cpus,
 
 	/* Try to power up all the CPUs that have been offlined. */
 	for_each_cpu(cpu, offlined_cpus) {
-		int ret = cpu_up(cpu);
+		int ret = add_cpu(cpu);
 
 		if (ret != 0) {
 			pr_err("Error occurred (%d) while trying "