qcacmn: Add qdf_opmode_str()

It is often useful to print the human readable version of an operating
mode in a log message or some other user-facing string. Add a function
for mapping QDF_OPMODE to human readable strings, qdf_opmode_str(), in
QDF such that various consumers do not have to implement it themselves.

Change-Id: I8756fb2ea97b3b8c7af2633b07694ad1e74d6d3e
CRs-Fixed: 2331888

qdf/inc/qdf_types.h

@@ -553,9 +553,20 @@ enum QDF_OPMODE {
 	QDF_WDS_MODE,
 	QDF_BTAMP_MODE,
 	QDF_AHDEMO_MODE,
+
+	/* Add new OP Modes to qdf_opmode_str as well */
+
 	QDF_MAX_NO_OF_MODE
 };
 
+/**
+ * qdf_opmode_str() - Return a human readable string representation of @opmode
+ * @opmode: The opmode to convert
+ *
+ * Return: string representation of @opmode
+ */
+const char *qdf_opmode_str(const enum QDF_OPMODE opmode);
+
 /**
  * enum QDF_GLOBAL_MODE - global mode when driver is loaded.
  *