mfd: twl6040: Cleanup in early error handling in probe function

The err: label is not needed we can just return instead of the jump there.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>