dt-bindings: pincfg-node: Add input-threshold-voltage-microvolt property

dt-bindings: pincfg-node: Add input-threshold-voltage-microvolt property

Add a generic pin configuration property
"input-threshold-voltage-microvolt" to support hardware designs where the
input logic threshold is decoupled from the power supply voltage.

This property allows the pinctrl driver to configure the correct internal
reference voltage for pins that need to accept input signals at a different
voltage level than their power supply. For example, a pin powered by 3.3V
may need to accept 1.8V logic signals.

This defines the reference for VIH (Input High Voltage) and VIL (Input Low
Voltage) thresholds, enabling proper signal detection across different
voltage domains.

Signed-off-by: Tzuyi Chang <tychang@realtek.com>
Co-developed-by: Yu-Chun Lin <eleanor.lin@realtek.com>
Signed-off-by: Yu-Chun Lin <eleanor.lin@realtek.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>