IMHO that is definitely a good solution to create a bunch of data (attributes) you need to use (access) in your presentation layer.
Thanks to this you are creating loosely coupled design in which the presentation layer (JSP) and business logic layer / controller (Servlet) are less dependent on each other.
By calling a servlet method from the JSP you are creating an additional dependency. I guess you could call this method using scripting (which is ultimately bad) or move the servlet calling code into the EL function which could do the work if you really, really need this.
So, the bottom line is that in your case I would certainly go for the attribute setting in Servlet class and JSP which accesses it. :-)