perf/core: introduced stub APIs for exported APIs

Introduced stub APIs for exported APIs so that we can build
independent module without any error if CONFIG_PERF_EVENT
feature is disabled in kernel.

drivers/platform/tegra/uncore_pmu/tegra23x_perf_uncore.c:
In function _scf_pmu_device_probe_:
drivers/platform/tegra/uncore_pmu/tegra23x_perf_uncore.c:596:    8:
error: implicit declaration of function _perf_pmu_register_
[-Werror=implicit-function-declaration]
  err = perf_pmu_register(&uncore_pmu->pmu, uncore_pmu->pmu.name,
531       |        ^~~~~~~~~~~~~~~~~
drivers/platform/tegra/uncore_pmu/tegra23x_perf_uncore.c: In
function _scf_pmu_device_remove_:
drivers/platform/tegra/uncore_pmu/tegra23x_perf_uncore.c:611:    2:
error: implicit declaration of function _perf_pmu_unregister_; did you
mean _device_unregister_? [-Werror=implicit-function-declaration]
  611 |  perf_pmu_unregister(&uncore_pmu->pmu);
      |  ^~~~~~~~~~~~~~~~~~~
      |  device_unregister
cc1: some warnings being treated as errors
scripts/Makefile.build:297: recipe for target
'drivers/platform/tegra/uncore_pmu/tegra23x_perf_uncore.o' failed
make[7]: *** [drivers/platform/tegra/
uncore_pmu/tegra23x_perf_uncore.o] Error 1

Signed-off-by: Manish Bhardwaj <bhardwajmanish18@gmail.com>

include/linux/perf_event.h

@@ -1679,6 +1679,42 @@ extern int perf_event_account_interrupt(struct perf_event *event);
 extern int perf_event_period(struct perf_event *event, u64 value);
 extern u64 perf_event_pause(struct perf_event *event, bool reset);
 #else /* !CONFIG_PERF_EVENTS: */
+static void perf_event_addr_filters_sync(struct perf_event *event)		{ }
+static u64 perf_event_read_value(struct perf_event *event,
+				 u64 *enabled, u64 *running)
+{
+	return 0;
+}
+static void perf_event_update_userpage(struct perf_event *event)			{ }
+static void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)	{ }
+static void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)	{ }
+static void perf_report_aux_output_id(struct perf_event *event, u64 hw_id)		{ }
+static void perf_tp_event(u16 event_type, u64 count, void *record,
+			  int entry_size, struct pt_regs *regs,
+			  struct hlist_head *head, int rctx,
+			  struct task_struct *task)
+{
+}
+static int perf_pmu_register(struct pmu *pmu, const char *name, int type)
+{
+	return -1;
+}
+extern void perf_pmu_unregister(struct pmu *pmu)					{ }
+static struct perf_event *
+perf_event_create_kernel_counter(struct perf_event_attr *attr,
+				int cpu,
+				struct task_struct *task,
+				perf_overflow_handler_t callback,
+				void *context)
+{
+	return NULL;
+}
+static void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)		{ }
+static ssize_t perf_event_sysfs_show(struct device *dev, struct device_attribute *attr,
+			      char *page)
+{
+	return -1;
+}
 static inline void *
 perf_aux_output_begin(struct perf_output_handle *handle,
 		      struct perf_event *event)				{ return NULL; }