OMAP4: powerdomain data: add voltage domains

Add voltage domain name to indicate which voltagedomain each
powerdomain is in.

The fixed voltage domain like ldo_wakeup for emu and wkup power
domain is added too.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
[khilman@ti.com]: renamed wakeup domain: s/ldo_wakeup/wakeup/
Signed-off-by: Kevin Hilman <khilman@ti.com>