ARM: u300: delete remnant clkdev.h file

The U300 now uses common clk, delete this leftover.
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

arch/arm/mach-u300/include/mach/clkdev.h

-#ifndef __MACH_CLKDEV_H
-#define __MACH_CLKDEV_H
-
-int __clk_get(struct clk *clk);
-void __clk_put(struct clk *clk);
-
-#endif