mfd: Drop modifying mc13xxx driver's id_table in probe

This was introduced in commit

        876989d5

 (mfd: Add device tree probe support for mc13xxx)

for spi and later while introducing support for i2c copied to the i2c
driver.

Modifying driver details is very strange, for example probing an
mc13892 device (instantiated via dt) removes the driver's ability to
handle (traditionally probed) mc13783 devices in this case.
I'm not aware of any problems that make this hack necessary and if
there were some, they'd have to be fixed in the spi/i2c core, not in
a driver.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>