ARM: S3C64XX: add I2C dependencies where needed

The SMDK6410_WM1190_EV1 and SMDK6410_WM1192_EV1 add-on
cards select MFD_WM*_I2C, but they ignore the fact that I2C
may be compiled as a loadable module.

This patch adds a dependency on I2C, which means we avoid
the build errors, but can end up in a case where the options
are hidden from the user when I2C is turned off.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Kukjin Kim <kgene@kernel.org>