OPP: Adjust includes to remove of_device.h

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. Adjust the
include files with what was implicitly included by of_device.h (cpu.h and
of.h) and drop including of_device.h.
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20230329-dt-cpu-header-cleanups-v1-18-581e2605fe47@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>

drivers/opp/of.c

@@ -13,7 +13,7 @@
 #include <linux/cpu.h>
 #include <linux/errno.h>
 #include <linux/device.h>
-#include <linux/of_device.h>
+#include <linux/of.h>
 #include <linux/pm_domain.h>
 #include <linux/slab.h>
 #include <linux/export.h>