[Ada] Remove redundant protection against empty lists

Calls to First on No_List intentionally return Empty node, so explicit
guards against No_List are unnecessary. Code cleanup; semantics is
unaffected.

gcc/ada/

	* exp_code.adb (Setup_Asm_IO_Args): Remove guard against No_List.
	* par_sco.adb (Process_Decisions): Likewise.
	* sem_ch13.adb (Check_Component_List): Likewise.
	* sem_ch6.adb (FCL): Likewise.
4 files changed