clk: mxs: Include clk.h in C files that use it

Clock provider drivers generally shouldn't include clk.h because
it's the consumer API. The clk.h include is being included in all
mxs files because it's part of mxs/clk.h even though nothing
actually requires it in that file. Move the clk.h include to the
C files that are actually using it and remove the clk.h include
from the header file. The clkdev.h include isn't used either, so
drop it too.

Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>