ada: Avoid calling Resolve with Stand.Any_Fixed as the expected type

ada: Avoid calling Resolve with Stand.Any_Fixed as the expected type

When we call Resolve for an expression, we pass in the expected type
for that expression. In the absence of semantic errors, that expected type
should never be any of the "Any_xxx" types declared in stand.ads (e.g.,
Any_Array, Any_Numeric, Any_Real). In particular, it should never be Any_Fixed.
Fix a case in which this rule was being violated.

gcc/ada/ChangeLog:

	* sem_res.adb
	(Set_Mixed_Mode_Operand): If we are about to call Resolve
	passing in Any_Fixed as the expected type, then instead pass in
	the fixed point type of the other operand (i.e., B_Typ).