Convert CONFIG_SPL_ETH_SUPPORT to Kconfig

Move this option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/am43xx_evm_ethboot_defconfig b/configs/am43xx_evm_ethboot_defconfig
index b49e12a..6596fa3 100644
--- a/configs/am43xx_evm_ethboot_defconfig
+++ b/configs/am43xx_evm_ethboot_defconfig
@@ -1,9 +1,10 @@
 CONFIG_ARM=y
 CONFIG_AM43XX=y
 CONFIG_TARGET_AM43XX_EVM=y
-CONFIG_SYS_EXTRA_OPTIONS="SERIAL1,CONS_INDEX=1,NAND,SPL_ETH_SUPPORT"
+CONFIG_SYS_EXTRA_OPTIONS="SERIAL1,CONS_INDEX=1,NAND"
 CONFIG_VERSION_VARIABLE=y
 CONFIG_SPL=y
+CONFIG_SPL_ETH_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set
diff --git a/configs/pcm051_rev1_defconfig b/configs/pcm051_rev1_defconfig
index e31ec60..a35222b 100644
--- a/configs/pcm051_rev1_defconfig
+++ b/configs/pcm051_rev1_defconfig
@@ -4,6 +4,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="REV1"
 CONFIG_VERSION_VARIABLE=y
 CONFIG_SPL=y
+CONFIG_SPL_ETH_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set
diff --git a/configs/pcm051_rev3_defconfig b/configs/pcm051_rev3_defconfig
index 5774d6b..8377398 100644
--- a/configs/pcm051_rev3_defconfig
+++ b/configs/pcm051_rev3_defconfig
@@ -4,6 +4,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="REV3"
 CONFIG_VERSION_VARIABLE=y
 CONFIG_SPL=y
+CONFIG_SPL_ETH_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set
diff --git a/configs/pengwyn_defconfig b/configs/pengwyn_defconfig
index 804c821..681672e 100644
--- a/configs/pengwyn_defconfig
+++ b/configs/pengwyn_defconfig
@@ -1,8 +1,9 @@
 CONFIG_ARM=y
 CONFIG_TARGET_PENGWYN=y
 CONFIG_SPL_ENV_SUPPORT=y
-CONFIG_SPL=y
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SPL=y
+CONFIG_SPL_ETH_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set