davinci: Add support for multiple PSCs

The current code to support the DaVinci Power and Sleep Controller (PSC)
assumes that there is only one controller.  This assumption is no longer
valid so expand the support to allow greater than one PSC.

To accomplish this, put the base addresses for the PSCs in the SoC
infrastructure so it can be referenced by the PSC code.  This also
requires adding an extra parameter to davinci_psc_config() to specify
the PSC that is to be enabled/disabled.

Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>