staging: r8188eu: silent_reset_inprogress is never read

silent_reset_inprogress in struct sreset_priv is only written
but never read. Remove it.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211024180448.20624-2-martin@kaiser.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>