arm: dts: k3-am654-base-board: Limit Sd card to High speed modes

There's an issue with the base board in which the power cycle
circuit takes way longer to power down than expected by mmc core.
code. This prevents the card from enumerating in UHS modes.

Disable UHS modes for this board until a new board revision fixes
the issue.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>