usb: pch_udc: Fixed issue which does not work with g_serial

This PCH_UDC driver does not work normally when "Serial gadget" is used.
The receiving data of control transmission (EP0 Control OUT Transaction)
has not received correctly.

This patch fixed this issue.
The following was modified.
 - The buffer size.
 - The change processing of a receiving buffer
   (The temporary buffer and the buffer prepared by gadget).
 - The setup processing of a DMA descriptor.

Currently the PCH_UDC driver can work normally with "Serial gadget"
or "File-backed Storage Gadget".

Signed-off-by: Toshiharu Okada <toshiharu-linux@dsn.okisemi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>