PM / clk: export symbols for existing pm_clk_<...> API fcns

While trying to convert a DMA driver from bool to tristate, we
encountered the following:

ERROR: "pm_clk_add_clk" [drivers/dma/tegra210-adma.ko] undefined!
ERROR: "pm_clk_create" [drivers/dma/tegra210-adma.ko] undefined!
ERROR: "pm_clk_destroy" [drivers/dma/tegra210-adma.ko] undefined!
ERROR: "pm_clk_suspend" [drivers/dma/tegra210-adma.ko] undefined!
ERROR: "pm_clk_resume" [drivers/dma/tegra210-adma.ko] undefined!

Since in principle there is nothing preventing these functions
from being used in modular code as well as builtin, we add the
export of them.  We expand the scope to also include:

   pm_clk_add
   of_pm_clk_add_clks
   pm_clk_remove
   pm_clk_remove_clk
   pm_clk_init
   pm_clk_runtime_suspend
   pm_clk_runtime_resume
   pm_clk_add_notifier

...since these functions are also non-static and presumably form
part of the existing API used by other drivers that may become
modular in the future.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>