staging: r8188eu: remove if_ether.h header file

All constants, declarations and macros in if_ether.h are either
duplicated from <uapi/linux/if_ether.h> or unused. Remove the file
if_ether.h and its includes.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20210824123621.10801-2-straube.linux@gmail.com


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