decoder: Fix lt_ref increment in ih264d_fix_error_in_dpb

When removing common nodes from short term list if it present in long
term reference list, number of long term buffers was wrongly
incremented. Only decrement of short term buffer count is needed in
such a case.

Bug: 140561484
Bug: 140566606
Bug: 140699853
Bug: 144980954
Bug: 145859214

Test: poc in bug
Change-Id: Iebf7ee7ed65e7b2097a899577982806b03fc6e5d