pinctrl: renesas: r8a77990: Add support for AVB power-source

Add support for configuring the I/O voltage level of the Ethernet AVB
pins on the R-Car E3 SoC.  "PIN_VDDQ_AVB0" can be configured for 2.5V or
3.3V operation.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/57883cd2d94c7919dc0f0db07cf6169ca89538e6.1678271030.git.geert+renesas@glider.be