rockchip: move dt-coreboot uart distinction into param handling code

rockchip: move dt-coreboot uart distinction into param handling code

Rockchip platforms can be booted from either u-boot or coreboot.

So far the Coreboot-console was initizalized from a coreboot data struct
in the early_param2 callbacks and dt-based consoles with data from the
rockchip_get_uart_* functions.

But later code may also need this console information for example for
special suspend handling. To make this easy follow a suggestion from
Julius Werner and move the coreboot<->dt distinction into the
rockchip_get_uart_* functions, thus making correct data about the used
uart available to all Rockchip platform code at all times.

This includes a new rockchip_get_uart_clock as well, because while the
dt-platforms right now always just default the rate defined in a constant
Coreboot provides its own field for the clock rate and we don't want to
loose that information for the console init. Similarly the rk_uart_*
variables should move into the non-Coreboot code, to prevent them from
being marked as unused, which also requires the rk_get_uart_* functions
to move below the actual dt-parsing.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Change-Id: I278d595d2aa6c6864187fc8979a9fbff9814feac