mmc: rockchip_dw_mmc: Add support for rk3576

mmc: rockchip_dw_mmc: Add support for rk3576

The rk3576 uses a different base-compatible, as starting with this
generation, the clock phase tuning is done via registers inside
the mmc controller and not from inside the CRU.

In U-Boot we do not tune at all, so no other code changes are
necessary.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>