staging:iio:hmc5843: Drop I2C detection code

I2C is generally not probed for devices other than those commonly found
on architectures where device treeor board files are not used.  Note also
that this implementation does not fill in the name field of the
i2c_board_info structure as the documentation states it must.  Hence
it is unlikely anyone is actually using it.

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Shubhrajyoti Datta <shubhrajyoti@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>