perf/arm_pmu_platform: Use dev_err_probe() for IRQ errors

By virtue of using platform_irq_get_optional() under the covers,
platform_irq_count() needs the target interrupt controller to be
available and may return -EPROBE_DEFER if it isn't. Let's use
dev_err_probe() to avoid a spurious error log (and help debug any
deferral issues) in that case.
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/073d5e0d3ed1f040592cb47ca6fe3759f40cc7d1.1616774562.git.robin.murphy@arm.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/perf/arm_pmu_platform.c

@@ -6,6 +6,7 @@
  * Copyright (C) 2010 ARM Ltd., Will Deacon <will.deacon@arm.com>
  */
 #define pr_fmt(fmt) "hw perfevents: " fmt
+#define dev_fmt pr_fmt
 
 #include <linux/bug.h>
 #include <linux/cpumask.h>
@@ -100,10 +101,8 @@ static int pmu_parse_irqs(struct arm_pmu *pmu)
 	struct pmu_hw_events __percpu *hw_events = pmu->hw_events;
 
 	num_irqs = platform_irq_count(pdev);
-	if (num_irqs < 0) {
-		pr_err("unable to count PMU IRQs\n");
-		return num_irqs;
-	}
+	if (num_irqs < 0)
+		return dev_err_probe(&pdev->dev, num_irqs, "unable to count PMU IRQs\n");
 
 	/*
 	 * In this case we have no idea which CPUs are covered by the PMU.