clk: h8s2678: Fix compile error

Recent cleanup removed some include files without checking if the cleaned
up code still compiles. This results in the following compile error.

drivers/clk/h8300/clk-h8s2678.c: In function ‘h8s2678_pll_clk_setup’:
drivers/clk/h8300/clk-h8s2678.c:99:14: error:
	implicit declaration of function ‘kzalloc’
drivers/clk/h8300/clk-h8s2678.c:138:2: error:
      implicit declaration of function ‘kfree’

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>

drivers/clk/h8300/clk-h8s2678.c

@@ -8,6 +8,7 @@
 #include <linux/err.h>
 #include <linux/device.h>
 #include <linux/of_address.h>
+#include <linux/slab.h>
 
 static DEFINE_SPINLOCK(clklock);