rockchip: rk3368: syscon: MSCH/PMUGRF/GRF support for OF_PLATDATA

rockchip: rk3368: syscon: MSCH/PMUGRF/GRF support for OF_PLATDATA

The RK3368 has both a limited TPL size (just 0x7000 bytes) and the
added challenge of booting in AArch64, which increases the code size
for TPL (particularily when using the LP64 programming model).  For
this reason we expect the RK3368 to always use OF_PLATDATA for its
TPL stage.

This change adds support for the MSCH, PMUGRF and GRF register regions
in syscon, which are necessary for initialising the RK3368's DRAM
controller.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>