[Ada] Remove redundant guard in checks for volatile actuals

[Ada] Remove redundant guard in checks for volatile actuals

When flagging names of volatile objects occurring in actual parameters
we guard against identifiers without entity. This is redundant, because
earlier in the resolution of actual parameters we already guard against
actuals with Any_Type.

Code cleanup related to handling of volatile components; behaviour is
unaffected.

gcc/ada/

	* sem_res.adb (Flag_Effectively_Volatile_Objects): Remove
	redundant guard.