i2c: remove u300 bus driver

The ST-Ericsson U300 platform is getting removed, so this driver is no
longer needed.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>