gst/selector/gstinputselector.c: Reuse the get_linked_pads for both source and sinkpa...

gst/selector/gstinputselector.c: Reuse the get_linked_pads for both source and sinkpads because they are the same.

Original commit message from CVS:
* gst/selector/gstinputselector.c: (gst_input_selector_init),
(gst_input_selector_event), (gst_input_selector_query):
Reuse the get_linked_pads for both source and sinkpads because they are
the same.
Implement a custum event handler and get the internally linked pad
directly instead of relying on the default (slower) implementation.