staging: r8188eu: remove kernel version depended code paths

Remove kernel version depended code paths from the driver.
Reported by checkpatch.

WARNING: LINUX_VERSION_CODE should be avoided, code should be for the version to which it is merged

Acked-by: Martin Kaiser <martin@kaiser.cx>
Acked-by: Phillip Potter <phil@philpotter.co.uk>
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20210815102406.3707-1-straube.linux@gmail.com


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