clk: Provide notifier stubs when !COMMON_CLK

The clk notifier symbols are hidden by COMMON_CLK.  However on some
platforms HAVE_CLK might be set while COMMON_CLK not which leads to
compile test build errors like:

$ make.cross ARCH=sh
   drivers/devfreq/tegra-devfreq.c: In function 'tegra_actmon_rate_notify_cb':
>> drivers/devfreq/tegra-devfreq.c:391:16: error: 'POST_RATE_CHANGE' undeclared (first use in this function)
     if (action != POST_RATE_CHANGE)
                   ^
   drivers/devfreq/tegra-devfreq.c: In function 'tegra_devfreq_probe':
>> drivers/devfreq/tegra-devfreq.c:654:8: error: implicit declaration of function 'clk_notifier_register' [-Werror=implicit-function-declaration]
     err = clk_notifier_register(tegra->emc_clock, &tegra->rate_change_nb);
           ^

Export the macros and data type declarations outside of COMMON_CLK ifdef
and provide stubs to fix the compile testing.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

include/linux/clk.h

@@ -20,8 +20,6 @@ struct device;
 
 struct clk;
 
-#ifdef CONFIG_COMMON_CLK
-
 /**
  * DOC: clk notifier callback types
  *
@@ -78,6 +76,8 @@ struct clk_notifier_data {
 	unsigned long		new_rate;
 };
 
+#ifdef CONFIG_COMMON_CLK
+
 /**
  * clk_notifier_register: register a clock rate-change notifier callback
  * @clk: clock whose rate we are interested in
@@ -140,6 +140,18 @@ bool clk_is_match(const struct clk *p, const struct clk *q);
 
 #else
 
+static inline int clk_notifier_register(struct clk *clk,
+					struct notifier_block *nb)
+{
+	return -ENOTSUPP;
+}
+
+static inline int clk_notifier_unregister(struct clk *clk,
+					  struct notifier_block *nb)
+{
+	return -ENOTSUPP;
+}
+
 static inline long clk_get_accuracy(struct clk *clk)
 {
 	return -ENOTSUPP;