mmc: rockchip_sdhci: Gate clock for glitch free phase switching

mmc: rockchip_sdhci: Gate clock for glitch free phase switching

Enable clock stopping to gate clock during phase code change to ensure
glitch free phase switching in auto-tuning circuit. Fixes HS200 mode
on RK3528.

POST_CHANGE_DLY
Time taken for phase switching and stable clock output.
- Less than 4-cycle latency

PRE_CHANGE_DLY
Maximum Latency specification between transmit clock and receive clock.
- Less than 4-cycle latency

TUNE_CLK_STOP_EN
Clock stopping control for Tuning and auto-tuning circuit. When enabled,
clock gate control output is pulled low before changing phase select
codes. This effectively stops the receive clock. Changing phase code
when clocks are stopped ensures glitch free phase switching.
- Clocks stopped during phase code change

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>