MAINTAINERS: add include/dt-bindings/clock to COMMON CLK FRAMEWORK

Maintainers of the directory Documentation/devicetree/bindings/clock
are also the maintainers of the corresponding directory in
include/dt-bindings/clock.

Add the file entry for include/dt-bindings/clock to the appropriate
section in MAINTAINERS.

Signed-off-by: Lukas Bulwahn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

MAINTAINERS

···
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git
 F:	Documentation/devicetree/bindings/clock/
 F:	drivers/clk/
+F:	include/dt-bindings/clock/
 F:	include/linux/clk-pr*
 F:	include/linux/clk/
 F:	include/linux/of_clk.h