MAINTAINERS: add entry for OMAP powerdomain/clockdomain per-SoC layer support

Add Rajendra Nayak and myself as maintainers for the OMAP
powerdomain/clockdomain per-SoC layer code.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Benoît Cousson <b-cousson@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>