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 <[e-mail]>
Signed-off-by: Stratos Karafotis <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/cpufreq.c

···
 }
 EXPORT_SYMBOL_GPL(cpufreq_cpu_put);
 
-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;
-}
-EXPORT_SYMBOL_GPL(cpufreq_next_valid);
-
 /*********************************************************************
  *            EXTERNALLY AFFECTING FREQUENCY CHANGES                 *
  *********************************************************************/

include/linux/cpufreq.h

···
 }
 #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