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/MPC837XERDB_defconfig b/configs/MPC837XERDB_defconfig
index 16d4251..192bcae 100644
--- a/configs/MPC837XERDB_defconfig
+++ b/configs/MPC837XERDB_defconfig
@@ -5,6 +5,7 @@
 CONFIG_ENV_SECT_SIZE=0x10000
 CONFIG_DEFAULT_DEVICE_TREE="mpc8379erdb"
 CONFIG_SYS_CLK_FREQ=66666667
+# CONFIG_SYS_PCI_64BIT is not set
 CONFIG_MPC83xx=y
 CONFIG_HIGH_BATS=y
 CONFIG_TARGET_MPC837XERDB=y