staging: rtl8188eu: remove a write-only power-index members

Remove power index members of struct hal_data_8188e that are written to
but never read.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210612180019.20387-4-martin@kaiser.cx


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