net: phy: mediatek: init val in .phy_led_polarity_set for AN7581

Fix smatch warning for uninitialised val in .phy_led_polarity_set for
AN7581 driver.

Correctly init to 0 to set polarity high by default.

Reported-by: Simon Horman <horms@kernel.org>
Fixes: 6a325aed ("net: phy: mediatek: add Airoha PHY ID to SoC driver")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://patch.msgid.link/20250415105313.3409-1-ansuelsmth@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>