OMAP: DSS2: Fix init and unit sequence

The initialization order of the DSS modules is important when pm_runtime
support is implemented. Currently RFBI is initialized before DISPC,
which will cause problems with pm_runtime as RFBI uses DISPC.

The same goes for uninitialization order, and dss_uninit needs to be
called last, and dispc_uninit just before that.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>