i2c: at91_i2c: remove the .probe_chip function

i2c: at91_i2c: remove the .probe_chip function

The .probe_chip function is supposed to probe an i2c device on the bus to
determine whether a device is answering to a particular address.
at91_i2c_probe_chip() did not do anything resembling this and always
returned 0.

It looks as though at91_i2c_probe_chip() was intended to be a .probe
function for the controller, as it was copied-and-pasted to become
at91_i2c_probe() in 0bc8f640a4d7ed.

Removing the at91_i2c_probe_chip() function makes the higher layer
(i2c_probe_chip()) try a zero-length read transfer to test for the
presence of a device instead, which does work.

Signed-off-by: Alan Ott <alan@softiron.com>
Acked-by: Wenyou Yang <wenyou.yang@microchip.com>
Reviewed-by: Heiko Schocher <hs@denx.de>