drivers: net: davinci_cpdma: double free on error

We recently change the kzalloc() to devm_kzalloc() so freeing "ctlr"
here could lead to a double free.

Fixes: e1943128

 ('drivers: net: davinci_cpdma: Convert kzalloc() to devm_kzalloc().')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>