arm: dts: socfpga: agilex5: Upgrade SDHCI controller from SD4HC to SD6HC

Upgrade the SDHCI Cadence controller from SD4HC to SD6HC for Agilex5
platform to support the newer controller version with enhanced features.

Key changes:
- Remove combophy0 node and associated references as SD6HC doesn't require
  separate PHY configuration node
- Upgrade MMC controller compatible from "cdns,sd4hc" to "cdns,sd6hc"
- Add Agilex5-specific compatible string "altr,agilex5-sd6hc" for
  platform-specific optimizations

Hardware configuration updates:
- Add voltage regulator support:
  * sd_emmc_power: Fixed 3.3V regulator for card power supply
  * sd_io_1v8_reg: GPIO-controlled regulator for 1.8V/3.3V I/O switching
- Configure proper reset control with named resets including combophy
  reset
- Add GPIO control via portb pin 3 for voltage switching

SD card operation:
- Configure for SD card specific operation (no-mmc, cap-sd-highspeed)
- Set maximum frequency to 200MHz
- Configure timing parameters for SD modes:
  * Default Speed (DS) and UHS-I SDR12 mode timing:
  * High Speed and UHS-I SDR25 mode timing:
- Add PHY timing delays for optimal signal integrity

Signed-off-by: Tanmay Kathpalia <[email protected]>
Reviewed-by: Tien Fong Chee <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/mmc/sdhci-cadence.c b/drivers/mmc/sdhci-cadence.c
index 7d169efa476..6cdb7f95cc5 100644
--- a/drivers/mmc/sdhci-cadence.c
+++ b/drivers/mmc/sdhci-cadence.c
@@ -260,6 +260,7 @@ static int sdhci_cdns_probe(struct udevice *dev)
 static const struct udevice_id sdhci_cdns_match[] = {
 	{ .compatible = "socionext,uniphier-sd4hc" },
 	{ .compatible = "cdns,sd4hc" },
+	{ .compatible = "altr,agilex5-sd6hc" },
 	{ .compatible = "cdns,sd6hc" },
 	{ /* sentinel */ }
 };