drivers/clk: appropriate __init annotation for const data

Init data marked const should be annotated with __initconst for
correctness and not __initdata.  This also fixes LTO builds that
otherwise fail with section mismatch errors.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
[sboyd@codeaurora.org: Dropped hunks that moved const char *
arrays to const char * const]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>