net: Move CONFIG_SPL_NET_VCI_STRING into Kconfig

This patch also adds the SPL time VCI string into Kconfig.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/am335x_evm_usbspl_defconfig b/configs/am335x_evm_usbspl_defconfig
index eee5e9b..cba5e84 100644
--- a/configs/am335x_evm_usbspl_defconfig
+++ b/configs/am335x_evm_usbspl_defconfig
@@ -38,3 +38,4 @@
 CONFIG_G_DNL_VENDOR_NUM=0x0451
 CONFIG_G_DNL_PRODUCT_NUM=0xd022
 CONFIG_OF_LIBFDT=y
+CONFIG_SPL_NET_VCI_STRING="AM335x U-Boot SPL"