arm: samsung: Convert s5p_goni and smdkc100 to DM_I2C

These are the last two samsung boards that don't use DM_I2C. Move them
over, leaving #ifdefs to allow the maintainer to complete this work.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>