Revert "mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch"

Revert "mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch"

This reverts commit 941a7abd4666912b84ab209396fdb54b0dae685d.

This commit uses presence of device-tree properties vmmc-supply and
vqmmc-supply for deciding whether to enable a quirk affecting timing of
clock and data.
The intention was to address issues observed with eMMC and SD on AM62
platforms.

This new quirk is however also enabled for AM64 breaking microSD access
on the SolidRun HimmingBoard-T which is supported in-tree since v6.11,
causing a regression. During boot microSD initialization now fails with
the error below:

[    2.008520] mmc1: SDHCI controller on fa00000.mmc [fa00000.mmc] using ADMA 64-bit
[    2.115348] mmc1: error -110 whilst initialising SD card

The heuristics for enabling the quirk are clearly not correct as they
break at least one but potentially many existing boards.

Revert the change and restore original behaviour until a more
appropriate method of selecting the quirk is derived.

Fixes: 941a7abd4666 ("mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch")
Closes: https://lore.kernel.org/linux-mmc/a70fc9fc-186f-4165-a652-3de50733763a@solid-run.com/
Cc: stable@vger.kernel.org
Signed-off-by: Josua Mayer <josua@solid-run.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20250127-am654-mmc-regression-v2-1-9bb39fb12810@solid-run.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>