staging: sw_sync: Add stubs for kernels without CONFIG_SW_SYNC

Add stubs for kernels without CONFIG_SW_SYNC

Cc: Colin Cross <[e-mail]>
Cc: Android Kernel Team <[e-mail]>
Signed-off-by: Greg Hackmann <[e-mail]>
[jstultz: resolved minor conflict, tweaked commit message]
Signed-off-by: John Stultz <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/android/sw_sync.h

···
 	u32			value;
 };
 
+#if IS_ENABLED(CONFIG_SW_SYNC)
 struct sw_sync_timeline *sw_sync_timeline_create(const char *name);
 void sw_sync_timeline_inc(struct sw_sync_timeline *obj, u32 inc);
 
 struct sync_pt *sw_sync_pt_create(struct sw_sync_timeline *obj, u32 value);
+#else
+static inline struct sw_sync_timeline *sw_sync_timeline_create(const char *name)
+{
+	return NULL;
+}
+
+static inline void sw_sync_timeline_inc(struct sw_sync_timeline *obj, u32 inc)
+{
+}
+
+static inline struct sync_pt *sw_sync_pt_create(struct sw_sync_timeline *obj,
+		u32 value)
+{
+	return NULL;
+}
+#endif /* IS_ENABLED(CONFIG_SW_SYNC) */
 
 #endif /* __KERNEL __ */