i2c: s6000: remove duplicate driver

It turned out that the s6000 simply has a designware IP core and should
use the designated driver for it which is way more maintained and
feature complete. There are currently no users in tree, and not even a
toolchain for s6000 seems to be available. So, simply remove this
duplicate. If someone needs assistance in converting to the designware
driver, the i2c list will be there to help.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>