sandbox: Tidy up I2C options

At present we enable the sandbox I2C driver for all builds. Add a separate
Kconfig option to control this, so that it can be disabled in TPL, where
it is not needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Schocher <hs@denx.de>
1 file changed