ARM: ux500: Enable the clock controlling Ethernet on Snowball

This fixes a regression introduced by common clk enablement.

On some u8500 based boards, the FMSC clock which is usually used
for flash, is wired up to the SMSC911x Ethernet driver. However,
the SMSC911x doesn't have common clk support yet, rendering it
unusable. Prior to the introduction of common clk the FMSC clock
was default on; however, common clk disables all clocks by default
and insists drivers take responsibility to enable theirs.

This fix enables the FMSC clock on Snowball, subsequently turning
on the SMSC911x Ethernet chip. It will be removed when the driver
is compatible with common clk.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>