clk: Silence sparse warnings about __clk_{get,put}()

drivers/clk/clk.c:2700:5: warning: symbol '__clk_get' was not declared. Should it be static?
drivers/clk/clk.c:2713:6: warning: symbol '__clk_put' was not declared. Should it be static?

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>