net: phy: phy_device: Fix PHY LED blinking code comment

Fix copy-paste error in the code comment. The code refers to
LED blinking configuration, not brightness configuration. It
was likely copied from comment above this one which does
refer to brightness configuration.

Fixes: 4e901018

 ("net: phy: phy_device: Call into the PHY driver to set LED blinking")
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20240626030638.512069-1-marex@denx.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>