usb: dwc2: clip max_transfer_size to 65535

Clip max_transfer_size to 65535 for host. dwc2_hc_setup_align_buf()
allocates coherent buffers with this size, and if it's too large we
can exhaust the coherent DMA pool.

Tested on Raspberry Pi and Altera SOCFPGA.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>