clk: WARN_ON about to disable a critical clock

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1455225554-13267-3-git-send-email-mturquette@baylibre.com