drivers/bus: arm-cci: fix build warnings

When the arm-cci driver is enabled, but both CONFIG_ARM_CCI5xx_PMU and
CONFIG_ARM_CCI400_PMU are not, we get a warning about how parts of
the driver are never used:

drivers/perf/arm-cci.c:1454:29: error: 'cci_pmu_models' defined but not used [-Werror=unused-variable]
drivers/perf/arm-cci.c:693:16: error: 'cci_pmu_event_show' defined but not used [-Werror=unused-function]
drivers/perf/arm-cci.c:685:16: error: 'cci_pmu_format_show' defined but not used [-Werror=unused-function]

Marking all three functions as __maybe_unused avoids the warnings in
randconfig builds. I'm doing this lacking any ideas for a better fix.

Fixes: 3de6be7a3dd8 ("drivers/bus: Split Arm CCI driver")
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/perf/arm-cci.c

@@ -120,9 +120,9 @@ enum cci_models {
 
 static void pmu_write_counters(struct cci_pmu *cci_pmu,
 				 unsigned long *mask);
-static ssize_t cci_pmu_format_show(struct device *dev,
+static ssize_t __maybe_unused cci_pmu_format_show(struct device *dev,
 			struct device_attribute *attr, char *buf);
-static ssize_t cci_pmu_event_show(struct device *dev,
+static ssize_t __maybe_unused cci_pmu_event_show(struct device *dev,
 			struct device_attribute *attr, char *buf);
 
 #define CCI_EXT_ATTR_ENTRY(_name, _func, _config) 				\
@@ -1451,7 +1451,7 @@ static int cci_pmu_offline_cpu(unsigned int cpu)
 	return 0;
 }
 
-static struct cci_pmu_model cci_pmu_models[] = {
+static __maybe_unused struct cci_pmu_model cci_pmu_models[] = {
 #ifdef CONFIG_ARM_CCI400_PMU
 	[CCI400_R0] = {
 		.name = "CCI_400",