staging: r8188eu: remove unnedeed parentheses in usbctrl_vendorreq()

Remove unneeded parentheses around a test for -ESHUTDOWN in
usbctrl_vendorreq().

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/20210919235356.4151-6-fmdefrancesco@gmail.com


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