net: phy: Fix reading LED reg property

'reg' is always encoded in 32 bits, thus it has to be read using the
function with the corresponding bit width.

Fixes: 01e5b728 ("net: phy: Add a binding for PHY LEDs")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230424141648.317944-1-alexander.stein@ew.tq-group.com


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