When discovering violation of the No_Elaboration_Code restriction it is
enough to find one unit that violates it; we don't need to examine all
units.

Code cleanup; semantics is unaffected.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* lib-writ.adb (Write_ALI): Exit from loop after seeing first
	unit that violates No_Elaboration_Code restriction.