am335x_evm: Drop CONFIG_SPL_ETH_SUPPORT from default build

On the boards this target supports this option is either non possible
without hardware mods (Beaglebone White/Black) or not supported due to
board design.  Drop this and regain some space.

Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/include/configs/am335x_evm.h b/include/configs/am335x_evm.h
index 2020e7f..884a42b 100644
--- a/include/configs/am335x_evm.h
+++ b/include/configs/am335x_evm.h
@@ -208,9 +208,6 @@
 #define CONFIG_BOOTCOUNT_LIMIT
 #define CONFIG_BOOTCOUNT_AM33XX
 
-/* CPSW support */
-#define CONFIG_SPL_ETH_SUPPORT
-
 /* USB gadget RNDIS */
 #define CONFIG_SPL_MUSB_NEW_SUPPORT