[Ada] Remove redundant guards for empty list

Routine Has_Excluded_Declaration iterates over declarations with
First/Present/Next, which is safe when declarations are No_List.

Cleanup related to excessive inlining-for-proof by GNATprove.

gcc/ada/

	* inline.adb (Build_Body_To_Inline): Remove redundant guards.
	* sem_ch6.adb (Analyze_Subprogram_Body_Helper): Likewise.

gcc/ada/inline.adb

@@ -1330,9 +1330,7 @@ package body Inline is
          return;
       end if;
 
-      if Present (Declarations (N))
-        and then Has_Excluded_Declaration (Spec_Id, Declarations (N))
-      then
+      if Has_Excluded_Declaration (Spec_Id, Declarations (N)) then
          return;
       end if;
 
@@ -2622,9 +2620,7 @@ package body Inline is
 
       --  Check excluded declarations
 
-      elsif Present (Declarations (N))
-        and then Has_Excluded_Declaration (Spec_Id, Declarations (N))
-      then
+      elsif Has_Excluded_Declaration (Spec_Id, Declarations (N)) then
          return;
 
       --  Check excluded statements. There is no need to protect us against
@@ -4388,9 +4384,7 @@ package body Inline is
             return True;
 
          elsif Nkind (S) = N_Block_Statement then
-            if Present (Declarations (S))
-              and then Has_Excluded_Declaration (Subp, Declarations (S))
-            then
+            if Has_Excluded_Declaration (Subp, Declarations (S)) then
                return True;
 
             elsif Present (Handled_Statement_Sequence (S)) then

gcc/ada/sem_ch6.adb

@@ -4931,9 +4931,7 @@ package body Sem_Ch6 is
                      --  by the GCC backend (ie. "function might not be
                      --  inlinable").
 
-                     if Present (Subp_Decl)
-                       and then Has_Excluded_Declaration (Spec_Id, Subp_Decl)
-                     then
+                     if Has_Excluded_Declaration (Spec_Id, Subp_Decl) then
                         null;
 
                      elsif Has_Excluded_Statement