Convert CONFIG_CONS_INDEX to Kconfig

This converts the following to Kconfig:
   CONFIG_CONS_INDEX

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/x530_defconfig b/configs/x530_defconfig
index de077cb..2f1fd75 100644
--- a/configs/x530_defconfig
+++ b/configs/x530_defconfig
@@ -70,6 +70,7 @@
 CONFIG_PCI_MVEBU=y
 CONFIG_DM_RTC=y
 CONFIG_RTC_DS1307=y
+CONFIG_SPECIFY_CONSOLE_INDEX=y
 CONFIG_DEBUG_UART_SHIFT=2
 CONFIG_SYS_NS16550=y
 CONFIG_KIRKWOOD_SPI=y