staging: r8188eu: remove EFUSE_ShadowRead()

Function EFUSE_ShadowRead() is not used, remove it. It is the only
user of the functions efuse_ShadowRead{1,2,4}Byte, remove these as
well.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20210922200420.9693-2-straube.linux@gmail.com


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