diag: Read data over peripherals in case of memory device mode

In case of usb disconnect, the logging mode needs to be checked
accordingly to decide whether the data needs to be read over
peripherals or not. In case of memory device mode the data needs
to be read continuoulsy over smd channel even if the usb is
disconnected.

Change-Id: I963740bc3b66a77c2ef68a2c58b48a5c7ed0ab0b
Signed-off-by: Katish Paran <kparan@codeaurora.org>