The s6105-ipcam driver calls i2c_register_board_info() which means that
not only does it need I2C to be enabled to be built but since that
symbol is not exported it means that the driver also can't be linked as
a module.  Use a bool instead of a tristate and add a dependency on I2C
to fix these issues.

Commit b5dd60fd (ASoC: s6000: Allow to build when COMPILE_TEST is
enabled) made this problem more visible since it enabled build of the
driver on more common architectures but this has always been an issue.
Signed-off-by: Mark Brown <broonie@linaro.org>