arm/dt: 8610: Set swfi_latency to prevent idle standalone PC

Allowing idle standalone power collapse (PC) with USB peripheral mode
will degrade mass storage performance numbers. Hence set swfi_latency
to one to vote for DMA latency to prevent standalone idle PC when
USB peripheral cable is connected.

CRs-Fixed: 491409
Change-Id: I76b1072de3a5efd8215b6143078e107ff68db435
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>