clk: Provide notifier stubs when !COMMON_CLK

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>