arm: MediaTek: add ethernet support for MT7623 boards

Enable ethernet related configs to mt7623n_bpir2_defconfig.
Add default IP addresses.
Enable noncached memory region required by ethernet driver.

diff --git a/configs/mt7623n_bpir2_defconfig b/configs/mt7623n_bpir2_defconfig
index ae4fb28..53ac63e 100644
--- a/configs/mt7623n_bpir2_defconfig
+++ b/configs/mt7623n_bpir2_defconfig
@@ -28,6 +28,7 @@
 CONFIG_CMD_FS_GENERIC=y
 CONFIG_OF_EMBED=y
 CONFIG_DEFAULT_DEVICE_TREE="mt7623n-bananapi-bpi-r2"
+CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_REGMAP=y
 CONFIG_SYSCON=y
 # CONFIG_BLOCK_CACHE is not set
@@ -37,6 +38,11 @@
 # CONFIG_MMC_QUIRKS is not set
 CONFIG_MMC_HS400_SUPPORT=y
 CONFIG_MMC_MTK=y
+CONFIG_DM_RESET=y
+CONFIG_RESET_MEDIATEK=y
+CONFIG_PHY_FIXED=y
+CONFIG_DM_ETH=y
+CONFIG_MEDIATEK_ETH=y
 CONFIG_PINCTRL=y
 CONFIG_PINCONF=y
 CONFIG_PINCTRL_MT7623=y