usb: chipidea: add xilinx zynq platform data

Due to having hardware tx buffers less than 512 bytes in size, streaming
must be enabled on the Zynq for the udc to work at all.  Add platform data
specific to the Zynq udc, which does not set the CI_HDRC_DISABLE_STREAMING
flag.

Based on a patch by the same name from the Xilinx vendor tree.

Signed-off-by: Nathan Sullivan <nathan.sullivan@ni.com>
Signed-off-by: Peter Chen <peter.chen@freescale.com>