staging: rtl8188eu: remove efuse write support

This driver does not need write access to the rtl1888eu chip's efuses.
Remove the code to set the voltages for writing the efuses.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210718173610.894-6-martin@kaiser.cx


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