arm/dt: 8226: Set swfi_latency to prevent idle standalone PC

Allowing idle standalone PC when cable connected will degrade
mass storage performance numbers. Hence set swfi_latency to one
to vote for DMA latency to prevent standalone idle PC when cable
is connected.

CRs-Fixed: 487046
Change-Id: I1a1e113f07bf88ca95de99165d630884d77dc095
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>