mmc: block: differentiate system suspend and shutdown flows

Block layer queue on suspend flow gives up if there are active requests,
while shutdown flow stops issuing thread and waits for completion of
outstanding requests and never give up.

This change propagates additional parameter to differentiate between
suspend and shutdown flows

Change-Id: I35a036c1a5585e3088301c07ade7d09ebd2cfc1b
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>