cpufreq: ppc: Add missing #include <asm/smp.h>

If CONFIG_SMP=n, <linux/smp.h> does not include <asm/smp.h>, causing:

drivers/cpufreq/ppc-corenet-cpufreq.c: In function 'corenet_cpufreq_cpu_init':
drivers/cpufreq/ppc-corenet-cpufreq.c:173:3: error: implicit declaration of function 'get_hard_smp_processor_id' [-Werror=implicit-function-declaration]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/ppc-corenet-cpufreq.c

@@ -22,6 +22,8 @@
 #include <linux/smp.h>
 #include <sysdev/fsl_soc.h>
 
+#include <asm/smp.h>	/* for get_hard_smp_processor_id() in UP configs */
+
 /**
  * struct cpu_data - per CPU data struct
  * @parent: the parent node of cpu clock