Support MT7530 PHY link change interrupts, and enable for MT7621.
For external MT7530, a GPIO IRQ line is required, which is
board-specific, so it should be added to each DTS. In case the
interrupt-controller property is missing, it will fall back to
polling mode.
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
f9cfe7af1f