net: davinci_emac: Free clock after checking the frequency

We only use clk_get() to get the frequency, the rest is done by
the runtime PM calls. Let's free the clock too.

Cc: Brian Hutchinson <b.hutchman@gmail.com>
Cc: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: David S. Miller <davem@davemloft.net>