am335x, dfu: add DFU_MANIFEST_POLL_TIMEOUT to the siemens boards

am335x, dfu: add DFU_MANIFEST_POLL_TIMEOUT to the siemens boards

as the siemens boards use dfu for updating a nand ubi partition
add DFU_MANIFEST_POLL_TIMEOUT to them, so dfu host waits after
complete transfer of the new image for DFU_MANIFEST_POLL_TIMEOUT
ms before sending again an usb request. So the board have enough
time to erase rest of the nand sectors.

Signed-off-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>