cpufreq: sun50i: Add explicit include for cpu.h

Removing the include of cpu.h from of_device.h causes an error:

drivers/cpufreq/sun50i-cpufreq-nvmem.c:42:19: error: implicit declaration of function ‘get_cpu_device’; did you mean ‘get_device’? [-Werror=implicit-function-declaration]

As of_device.h is not otherwise needed, it can be replaced with of.h
(also implicitly included).
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20230329-dt-cpu-header-cleanups-v1-15-581e2605fe47@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>

drivers/cpufreq/sun50i-cpufreq-nvmem.c

@@ -10,9 +10,10 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/cpu.h>
 #include <linux/module.h>
 #include <linux/nvmem-consumer.h>
-#include <linux/of_device.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/pm_opp.h>
 #include <linux/slab.h>