staging: rts5208: Remove unused driver

staging: rts5208: Remove unused driver

Wei Wang from Realsil contributed this driver in 2011.

The following reasons lead to the removal:
- This driver generates maintenance workload
- Did not find minimal documentation on the web.
- No blog entries about anyone using the rts5208 and rts5288 during the
  last years.
- Did not find any device that may has it in and is still available on
  the market.

Link: https://lore.kernel.org/linux-staging/2024100943-shank-washed-a765@gregkh/T/#t
Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/20241009193250.6211-1-philipp.g.hortmann@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>