[PATCH][gdb/testsuite] Fix funcall_ref.exp xpass

[Tom Tromey]

>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:

Tom> 2020-02-18  Tom de Vries  <tdevries@suse.de>

Tom> 	* gdb.ada/funcall_ref.exp: Replace xfail setup by unsupported check.

Ok.  Thanks for doing this.  This is a nice way to do this kind of test.

Tom