staging: r8188eu: Remove a test from usbctrl_vendorreq()

Remove an unnecessary 'if' test from usbctrl_vendorreq() because
"length" is never greater than MAX_VENDOR_REQ_CMD_SIZE.

Co-developed-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Link: https://lore.kernel.org/r/20210924122705.3781-13-fmdefrancesco@gmail.com


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