Bluetooth: Reduce Obex MTU size for A2DP or SCO concurrency

Reduce Obex MTU to 8k from 64k when OPP send is tried with
SCO / A2DP streaming in progress, so that the continue response
for first complete Obex PUT packet is received from SOC within
50 seconds time frame.

CRs-Fixed: 571865
Change-Id: I014b4e173d9a78419eb0c6752ec03bf4b924e934