MAINTAINERS: Update clock binding entry for Actions Semi Owl SoCs

commit d0e45d68 ("dt-bindings: clock: Add S700 support for Actions
Semi Soc's")'

renamed the clock binding for Actions Semi Owl SoCs from
actions,s900-cmu.txt to actions,owl-cmu.txt inorder to accommodate all
members of Owl family SoCs. Hence, update the relevant entry in
MAINTAINERS file.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>