ARM: OMAP: clock: split plat/clkdev_omap.h into OMAP1/2 files

To facilitate the ARM single image work, split
arch/arm/plat-omap/include/plat/clkdev_omap.h into the
arch/arm/mach-omap1/clock.h and arch/arm/mach-omap2/clock.h files.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>