ARM: ux500: Rename references to the ccu9540 dev board accordingly

When enabling ST-Ericsson's ccu9540 development board the board's
full name has not been used. This patch adapts all references of
the board's short name to how it should be referenced.

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