rockchip: sdhci: Add HS400 Enhanced Strobe support for RK3399

On RK3399, a register bit must be set to enable Enhanced Strobe.
Let the Rockchip SDHCI driver set it when Enhanced Strobe configuration
is requested. However, having it set makes the lower-speed modes stop
working and makes reinitialization fail, so let it be unset as needed in
set_control_reg().

This is mostly ported from Linux's Arasan SDHCI driver which happens
to be the underlying IP. (drivers/mmc/host/sdhci-of-arasan.c in Linux
tree).

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>