drivers:usb: use get|put_unaligned_le16

This patch use get|put_unaligned_le16 to access structure data
to avoid data abort on some ARM platforms.

Signed-off-by: Piotr Wilczek <p.wilczek@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
CC: Marek Vasut <marex@denx.de>