OMAP powerdomain, hwmod, omap_device: add some credits

Add some missing credits for people who have contributed significant features
or fixes.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Benoît Cousson <b-cousson@ti.com>
Cc: Tero Kristo <tero.kristo@nokia.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Thara Gopinath <thara@ti.com>