clk: imx8mp: Include slab.h instead of clkdev.h

slab.h is necessary and included indirectly by clkdev.h,
actually, there is nothing in use from clkdev.h, so just
include slab.h instead of clkdev.h.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/clk/imx/clk-imx8mp.c

@@ -4,13 +4,13 @@
  */
 
 #include <dt-bindings/clock/imx8mp-clock.h>
-#include <linux/clkdev.h>
 #include <linux/clk-provider.h>
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
+#include <linux/slab.h>
 #include <linux/types.h>
 
 #include "clk.h"