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/stm32mp15_dhcom_basic_defconfig b/configs/stm32mp15_dhcom_basic_defconfig
index 8442f0b..c3e6b09 100644
--- a/configs/stm32mp15_dhcom_basic_defconfig
+++ b/configs/stm32mp15_dhcom_basic_defconfig
@@ -133,6 +133,7 @@
 CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_SPI_FLASH_MTD=y
+CONFIG_PHY_ANEG_TIMEOUT=20000
 CONFIG_DWC_ETH_QOS=y
 CONFIG_KS8851_MLL=y
 CONFIG_PHY=y