Rename gatt_primary_t to more generic name

The gatt_primary_t typedef was renamed to gatt_cb_t because it will be
used for primary and characteristic callbacks.
diff --git a/attrib/gatt.c b/attrib/gatt.c
index 7d09689..79d8b9d 100644
--- a/attrib/gatt.c
+++ b/attrib/gatt.c
@@ -35,7 +35,7 @@
 	GAttrib *attrib;
 	uuid_t uuid;
 	GSList *primaries;
-	gatt_primary_t cb;
+	gatt_cb_t cb;
 	void *user_data;
 };
 
@@ -193,7 +193,7 @@
 	discover_primary_free(dp);
 }
 
-guint gatt_discover_primary(GAttrib *attrib, uuid_t *uuid, gatt_primary_t func,
+guint gatt_discover_primary(GAttrib *attrib, uuid_t *uuid, gatt_cb_t func,
 							gpointer user_data)
 {
 	struct discover_primary *dp;
diff --git a/attrib/gatt.h b/attrib/gatt.h
index 936c592..0bdac77 100644
--- a/attrib/gatt.h
+++ b/attrib/gatt.h
@@ -24,9 +24,9 @@
 
 #define GATT_CID 4
 
-typedef void (*gatt_primary_t) (GSList *l, guint8 status, gpointer user_data);
+typedef void (*gatt_cb_t) (GSList *l, guint8 status, gpointer user_data);
 
-guint gatt_discover_primary(GAttrib *attrib, uuid_t *uuid, gatt_primary_t func,
+guint gatt_discover_primary(GAttrib *attrib, uuid_t *uuid, gatt_cb_t func,
 							gpointer user_data);
 
 guint gatt_discover_char(GAttrib *attrib, uint16_t start, uint16_t end,