diag: Clear masks upon logging exit

This patch clears the peripheral masks upon the mdlog exit
and USB disconnection. This enables to keep the data and
cmd channel open for read.

CRs-Fixed: 1057143
Change-Id: Ie6f19319b75f3bf389ddd5a8168fd3bcd3efbc8b
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>