clk: add non CONFIG_OF routines for clk-provider

Some drivers that are shared between architectures have HAVE_CLK selected
but don't have OF. To remove compilation errors for drivers that provide
clocks on DT with of_clk_add_provider we would have to enclose these calls
within #ifdef CONFIG_OF, #endif.

This patch adds some stubs for OF related clk-provider functions that
either do nothing or return appropriate values if CONFIG_OF is not set.
So, definition of these routines will always be available.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mike Turquette <mturquette@linaro.org>