i2c: i2c-sirf: Drop class based scanning to improve bootup time

This driver has been flagged to drop class based instantiation. The removal
improves boot-up time and is unneeded for embedded controllers. Users have been
warned to switch for some time now, so we can actually do the removal. Keep the
DEPRECATED flag, so the core can inform users that the behaviour finally
changed now. After another transition period, this flag can go, too.

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