clk: Add missing header for 'bool' definition to clk-conf.h

of_clk_set_defaults uses the type 'bool', but clk-conf.h does not
include its definition.

This results in a compile error when only clk-conf.h is used.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>