ada: Tweak condition for name resolution failure

ada: Tweak condition for name resolution failure

It is sometimes used as a convention across GNAT's code to set the Etype
field of a node to Any_Type to signal a name resolution error. This has
the potential to be confusing, which is why this patch replaces one such
use of the convention by a less convoluted check.

This only affects error recovery paths, and possibly doesn't change the
behavior of the compiler at all.

gcc/ada/ChangeLog:

	* sem_ch4.adb (Analyze_Selected_Component): Tweak condition.