staging: r8188eu: simplify the ps_processing check

It's sufficient to check pwrpriv->ps_processing as part of the while-loop.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220413193654.258507-4-martin@kaiser.cx


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