ARM: cpuidle: Drop of_device.h include

Now that of_cpu_device_node_get() is defined in of.h, of_device.h is just
implicitly including other includes, and is no longer needed. Just drop
including of_device.h as of.h is already included.

Link: https://lore.kernel.org/r/20230329-dt-cpu-header-cleanups-v1-7-581e2605fe47@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>

arch/arm/kernel/cpuidle.c

@@ -5,7 +5,6 @@
 
 #include <linux/cpuidle.h>
 #include <linux/of.h>
-#include <linux/of_device.h>
 #include <asm/cpuidle.h>
 
 extern struct of_cpuidle_method __cpuidle_method_of_table[];