In function xadc_probe, xadc_write_adc_reg can return an error value
when write fails. The fix checks for the return value consistent with
other invocations of the latter function.
Signed-off-by: NAditya Pakki <pakki001@umn.edu>
Reviewed-by: NMichal Simek <michal.simek@xilinx.com>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>