drivers: net: davinci_cpdma: Convert kzalloc() to devm_kzalloc().

Convert kzalloc() to devm_kzalloc().

Signed-off-by: George Cherian <george.cherian@ti.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>