[Ada] Simplify call to Unique_Defining_Entity on protected entry declarations

Calling Unique_Defining_Entity on protectected entry declarations is
equivalent to calling a simpler Defining_Entity; use the simpler routine.

Simplification only; semantics unaffected, so no test provided.

2018-05-31  Piotr Trojanek  <trojanek@adacore.com>

gcc/ada/

	* sem_prag.adb (Analyze_Pragma): Replace call to Unique_Defining_Entity
	with a semantically equivalent call to Defining_Entity.

From-SVN: r261003

gcc/ada/ChangeLog

 2018-05-31  Piotr Trojanek  <trojanek@adacore.com>
 
+	* sem_prag.adb (Analyze_Pragma): Replace call to Unique_Defining_Entity
+	with a semantically equivalent call to Defining_Entity.
+
+2018-05-31  Piotr Trojanek  <trojanek@adacore.com>
+
 	* sem_prag.adb (Analyze_Pragma): Set Etype on the rewritten
 	Max_Queue_Length expression.
 

gcc/ada/sem_prag.adb

@@ -18795,7 +18795,7 @@ package body Sem_Prag is
                   return;
                end if;
 
-               Entry_Id := Unique_Defining_Entity (Entry_Decl);
+               Entry_Id := Defining_Entity (Entry_Decl);
 
             --  Otherwise the pragma is associated with an illegal construct