add pio_usb_host_get_frame_number()

[hathach]

This PR add pio_usb_host_get_frame_number() which can be handy for tinyusb when doing delay without actually using any hw timer https://github.com/hathach/tinyusb/blob/master/src/host/usbh.c#L261

which I kind of forgot to add so far https://github.com/hathach/tinyusb/blob/master/src/portable/raspberrypi/pio_usb/hcd_pio_usb.c#L105

This also increase sof_count to 11-bit in SOF packet (previously 5-bit).

modification is originially written by @tannewt

screenshort with frame number wrap-around

[sekigon-gonnoc]

thanks!