The CCF implementations for the various shmobile SoCs don't use clkdev
functionality, hence drop the inclusion of <linux/clkdev.h>.

Add the missing #include <linux/slab.h>, which was included implicitly
through <asm/clkdev.h> before.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>