drivers: usb: dwc3: Remove xfer timer when going to suspend

When in the middle of processing bulk transfers we get a
suspend event, we still continue to arm the bulk transfer timer
because we didn't finish the bulk transfer.
However we are going to suspend initiated by the host (sleep),
and the device does go to LPM thus causing the transfer_complete
function running when clocks are off and resulting in unclocked access.
This patch makes sure we do pm_runtime_get the device before
accessing registers, and doesn't arm the timer again when we are
in suspend state.

CRs-fixed: 746587
Change-Id: I9491e360cd2ea29d569e2a8a7da771f29ec946b3
Signed-off-by: Lena Salman <esalman@codeaurora.org>