Change value_val_atr to ada_val_atr

Change value_val_atr to ada_val_atr

This renames value_val_atr to ada_val_atr, changing its parameters to
more closely mirror other expression helpers.  The
EVAL_AVOID_SIDE_EFFECTS case is moved into this function as well.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* ada-lang.c (ada_val_atr): Rename from value_val_atr.  Change
	parameters.
	(ada_evaluate_subexp): Use it.