Convert CONFIG_ENABLE_36BIT_PHYS to Kconfig

This converts the following to Kconfig:
   CONFIG_ENABLE_36BIT_PHYS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/MPC8548CDS_36BIT_defconfig b/configs/MPC8548CDS_36BIT_defconfig
index f2dd5d3..14eeef9 100644
--- a/configs/MPC8548CDS_36BIT_defconfig
+++ b/configs/MPC8548CDS_36BIT_defconfig
@@ -10,6 +10,7 @@
 # CONFIG_CMD_ERRATA is not set
 CONFIG_TARGET_MPC8548CDS=y
 CONFIG_MPC85XX_HAVE_RESET_VECTOR=y
+CONFIG_ENABLE_36BIT_PHYS=y
 CONFIG_PHYS_64BIT=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y