Fix TIYUV420PackSemiPlanor color converter to use src crop

TIYUV420PackSemiPlanor color conversion routine is updated to
offset src_y using the given crop parameters. Previously it was
assuming that the mBits were already offset but at least in the
latest code base it is not, so it needs to take into account
the src crop appropriately.

bug:70844660

Change-Id: I206925ba254cf547241ff30c6211b4dc94c9cac7
Signed-off-by: Angela Stegmaier <angelabaker@ti.com>