MAINTAINERS: Add linux/of_*.h headers to appropriate subsystems

The DeviceTree support code for specific subsystems are maintained by
the respective subsystem maintainers. However, only the DT
maintainers are listed for most of the linux/of_*.h headers. Fix this
and add the headers to the appropriate subsystem maintainer.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Joerg Roedel <joro@8bytes.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rob Herring <robh@kernel.org>