cpufreq: Fix build error on some platforms that use cpufreq_for_each_*

On platforms that use cpufreq_for_each_* macros, build fails if
CONFIG_CPU_FREQ=n, e.g. ARM/shmobile/koelsch/non-multiplatform:

drivers/built-in.o: In function `clk_round_parent':
clkdev.c:(.text+0xcf168): undefined reference to `cpufreq_next_valid'
drivers/built-in.o: In function `clk_rate_table_find':
clkdev.c:(.text+0xcf820): undefined reference to `cpufreq_next_valid'
make[3]: *** [vmlinux] Error 1

Fix this making cpufreq_next_valid function inline and move it to
cpufreq.h.

Fixes: 27e289dce297 (cpufreq: Introduce macros for cpufreq_frequency_table iteration)
Reported-and-tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 9d803b5..3f45889 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -489,8 +489,15 @@
 }
 #endif
 
-
-bool cpufreq_next_valid(struct cpufreq_frequency_table **pos);
+static inline bool cpufreq_next_valid(struct cpufreq_frequency_table **pos)
+{
+	while ((*pos)->frequency != CPUFREQ_TABLE_END)
+		if ((*pos)->frequency != CPUFREQ_ENTRY_INVALID)
+			return true;
+		else
+			(*pos)++;
+	return false;
+}
 
 /*
  * cpufreq_for_each_entry -	iterate over a cpufreq_frequency_table