diag: Add support for multi connection logging

This change adds support to route On-Device logging and
USB logging traffic per peripheral. A peripherals'
traffic can go to either endpoint but not both. The
mux layer has a peripheral state and the mode switching
logic has multi mode support.

CRs-Fixed: 1004236
Change-Id: I54fef744bdf08a346e4aef22c1280e928cdaf5d2
Signed-off-by: Chris Lew <clew@codeaurora.org>