net: phy: Replace PHY_ANEG_TIMEOUT with Kconfig symbol

Switch PHY_ANEG_TIMEOUT to CONFIG_PHY_ANEG_TIMEOUT Kconfig symbol.
This removes one more configuration headers option finalizes its
Kconfig symbol conversion. No functional change expected.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/configs/imx8ulp_evk_defconfig b/configs/imx8ulp_evk_defconfig
index 721c4cb..b302df1 100644
--- a/configs/imx8ulp_evk_defconfig
+++ b/configs/imx8ulp_evk_defconfig
@@ -74,6 +74,7 @@
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_MACRONIX=y
 CONFIG_PHYLIB=y
+CONFIG_PHY_ANEG_TIMEOUT=20000
 CONFIG_PHY_MICREL=y
 CONFIG_PHY_MICREL_KSZ8XXX=y
 CONFIG_FEC_MXC=y