arm64: dts: renesas: ulcb-kf: Adapt sound 5v regulator to schematics

Sound uses the standard 5V supply, so rename the fixed regulator as
such. Also add properties documenting it is always on, also during boot.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20240129212350.33370-3-wsa+renesas@sang-engineering.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>