Convert CONFIG_SYS_PCI_64BIT to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_PCI_64BIT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/socrates_defconfig b/configs/socrates_defconfig
index f2e9271..ea0224d 100644
--- a/configs/socrates_defconfig
+++ b/configs/socrates_defconfig
@@ -3,6 +3,7 @@
 CONFIG_ENV_SIZE=0x4000
 CONFIG_ENV_SECT_SIZE=0x20000
 CONFIG_DEFAULT_DEVICE_TREE="socrates"
+# CONFIG_SYS_PCI_64BIT is not set
 CONFIG_MPC85xx=y
 # CONFIG_CMD_ERRATA is not set
 CONFIG_TARGET_SOCRATES=y