MCAP: Add test interface ID (1/2)

* Some PTS tests requires protocols and profiles to be accessed at stack
  API level
* This CL creates an ID for the MCAP protocol
* An application must be able to reference stack headers in order to use
  such an interface

Bug: 37867299
Test: make, no user visible effect
Change-Id: Ice654321cdeb11f93b1c8fc4a0753fe86bd82a56
diff --git a/include/hardware/bluetooth.h b/include/hardware/bluetooth.h
index b706e8a..6e287e6 100644
--- a/include/hardware/bluetooth.h
+++ b/include/hardware/bluetooth.h
@@ -35,7 +35,7 @@
 #define BT_STACK_TEST_MODULE_ID "bluetooth_test"
 
 
-/* Bluetooth profile interface IDs */
+/** Bluetooth profile interface IDs */
 
 #define BT_PROFILE_HANDSFREE_ID "handsfree"
 #define BT_PROFILE_HANDSFREE_CLIENT_ID "handsfree_client"
@@ -52,6 +52,9 @@
 #define BT_PROFILE_AV_RC_ID "avrcp"
 #define BT_PROFILE_AV_RC_CTRL_ID "avrcp_ctrl"
 
+/** Bluetooth test interface IDs */
+#define BT_TEST_INTERFACE_MCAP_ID "mcap_test"
+
 /** Bluetooth Address */
 typedef struct {
     uint8_t address[6];