mfd: tps80031: Convert to devm_i2c_new_dummy_device

Move from i2c_new_dummy() to devm_i2c_new_dummy_device(). So, we now get
an ERRPTR which we use in error handling and we can skip removal of the
created devices.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>