TEST_MAPPING: Consolidate libstagefright's postmapping entries

libstagefright/TEST_MAPPING had two sets of postsubmit,
these are now consolidated to a single postsubmit block.

Bug: 304383609
Test: Treehugger

Change-Id: Idcf99b7d0f8029490d708691c7bac37627c17ccb
1 file changed