elan: Add umockdev based test

Unfortunately, the timeout handling cannot be simulated properly. This
also adds a workaround in the driver to not consider it a protocol error
if this happens.

tests/meson.build

@@ -29,6 +29,7 @@ if get_option('introspection')
     endif
 
     drivers_tests = [
+        'elan',
         'vfs5011',
         'synaptics',
     ]