net: ethernet: ti: cpsw: enable cpts irq

The CPSW misc IRQ need be enabled for CPTS event_pend IRQs processing. This
patch adds corresponding support to CPSW driver.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>