OMAP1 / PM: Use generic clock manipulation routines for runtime PM

Convert OMAP1 to using the new generic clock manipulation routines
and a device power domain for runtime PM instead of overriding the
platform bus type's runtime PM callbacks.  This allows us to simplify
OMAP1-specific code and to share some code with other platforms
(shmobile in particular).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Kevin Hilman <khilman@ti.com>