ada: Put_Image spec incorrectly ignored for Fixed_Point_Type'Base'Image call.

If a Put_Image aspect specification (introduced in Ada 2022) is given for a
fixed point type Fx, then in some cases a call to Fx'Base'Image would
incorrectly ignore the aspect specification and would instead return the
pre-Ada2022 version of the image. However, a call to Fx'Image would do the
right thing.

gcc/ada/ChangeLog:

	* exp_put_image.adb (Image_Should_Call_Put_Image): Cope with the case
	where the attribute prefix for an Image attribute reference
	denotes an Itype constructed for a fixed point type. Calling
	Has_Aspect with such an Itype misses applicable aspect
	specifications; we need to look on the right list. This comes up
	if the prefix of the attribute reference is
	Some_Fixed_Point_Type'Base.