optimize pcie_7x buffering for DMA
optimize pcie_7x buffering for DMA

Change-Id: Idadfb7436b57760f77bd059e58156d89e914cc8f

cambridgehackers/connectal,8l/connectal,chenm001/connectal,8l/connectal,hanw/connectal,cambridgehackers/connectal,csail-csg/connectal,csail-csg/connectal,chenm001/connectal,hanw/connectal,8l/connectal,chenm001/connectal,chenm001/connectal,hanw/connectal,csail-csg/connectal,csail-csg/connectal,chenm001/connectal,8l/connectal,cambridgehackers/connectal,hanw/connectal,cambridgehackers/connectal,8l/connectal,csail-csg/connectal,cambridgehackers/connectal,hanw/connectal