rockchip: rk3399: store actual debug uart information on suspend

rockchip: rk3399: store actual debug uart information on suspend

The rk3399 suspend code saves and restores the debug uart settings, but
right now always does this for the default uart. Right now this works
only by chance for the majority of rk3399 boards, which do not deviate
from that default.

But both Coreboot as well as U-Boot-based platforms can actually use
different uarts for their output, which can be configured from either
devicetree or Coreboot-variables.

To fix this, just use the stored uart-base information instead of the
default constant.

Signed-off-by: Heiko Stuebner <[email protected]>
Change-Id: I1ea059d59a1126f6f8702315df7e620e632b686e