dt-bindings: net: Move realtek,rtl9301-switch to net

dt-bindings: net: Move realtek,rtl9301-switch to net

Initially realtek,rtl9301-switch was placed under mfd/ because it had
some non-switch related blocks (specifically i2c and reset) but with a
bit more review it has become apparent that this was wrong and the
binding should live under net/.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Acked-by: Lee Jones <lee@kernel.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250218195216.1034220-2-chris.packham@alliedtelesis.co.nz
Signed-off-by: Jakub Kicinski <kuba@kernel.org>