Sema: add error for non-comptime param in comptime func

Adds error for taking a non comptime parameter in a function returning a
comptime-only type but not when that type is dependent on a parameter.

Co-authored-by: Veikka Tuominen <git@vexu.eu>

test/behavior/union.zig

@@ -745,7 +745,7 @@ fn setAttribute(attr: Attribute) void {
     _ = attr;
 }
 
-fn Setter(attr: Attribute) type {
+fn Setter(comptime attr: Attribute) type {
     return struct {
         fn set() void {
             setAttribute(attr);