staging: rtl8188eu: remove unnecessary brackets

ESHUTDOWN is just a number, it needs no brackets.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210407170531.29356-2-martin@kaiser.cx


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