Add comments for HANGUP request.

For bug #3136179

Clarify RIL should NOT report active connection for GET_CURRENT_CALLS

after HANGUP request returns.

Change-Id: Icf9cc14b7d9cbfee6552cf51a648432caac28ab1

include/telephony/ril.h

@@ -869,6 +869,9 @@ typedef struct {
  *
  * Hang up a specific line (like AT+CHLD=1x)
  *
+ * After this HANGUP request returns, RIL should show the connection is NOT
+ * active anymore in next RIL_REQUEST_GET_CURRENT_CALLS query.
+ *
  * "data" is an int *
  * (int *)data)[0] contains Connection index (value of 'x' in CHLD above)
  *
@@ -887,6 +890,9 @@ typedef struct {
  *
  * Hang up waiting or held (like AT+CHLD=0)
  *
+ * After this HANGUP request returns, RIL should show the connection is NOT
+ * active anymore in next RIL_REQUEST_GET_CURRENT_CALLS query.
+ *
  * "data" is NULL
  * "response" is NULL
  *
@@ -903,6 +909,9 @@ typedef struct {
  *
  * Hang up waiting or held (like AT+CHLD=1)
  *
+ * After this HANGUP request returns, RIL should show the connection is NOT
+ * active anymore in next RIL_REQUEST_GET_CURRENT_CALLS query.
+ *
  * "data" is NULL
  * "response" is NULL
  *