OMAP2: powerdomain: Add break in switch statement

Add a missing break at end of switch statement. At the moment it is a
fall through to WARN_ON(1) and return -EEXIST.

Signed-off-by: Thomas Weber <weber@corscience.de>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>