dwc3: gadget: Improve TX FIFO resize functionality

This change considers USB device speed to set max_packet size
instead of provided max_packet value from USB function driver.
It doesn't resize ep0IN TxFIFO, and starts with ep1IN TxFIFO only.

Change-Id: Ifce63f5a8570f79bad1e5d3ae6f5d580c34046b5
Signed-off-by: Mayank Rana <mrana@codeaurora.org>