staging: r8188eu: remove shared buffer for USB requests

Remove the shared buffer for USB requests because it is not necessary
and use a local on stack variable since the new Core USB API does not
have the constraints of usb_control_msg().

Co-developed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/20210924122705.3781-16-fmdefrancesco@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>