staging: r8188eu: introduce new core dir for RTL8188eu driver

This patchset is split in order to keep the file sizes down. This core
directory is part of the newer/better driver from GitHub modified by
Larry Finger. Import this as the basis for all future work going
forward.

Suggested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210727232219.2948-2-phil@philpotter.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>