mpc83xx: Get rid of CONFIG_83XX_CLKIN

MPC83xx uses CONFIG_83XX_CLKIN instead of CONFIG_SYS_CLK_FREQ to set the
system clock. To migrate the architecture, we can replace
CONFIG_83XX_CLKIN with CONFIG_SYS_CLK_FREQ.

To do this
* replace all occurrences of CONFIG_83XX_CLKIN with CONFIG_SYS_CLK_FREQ
* set CONFIG_SYS_CLK_FREQ to the old value of CONFIG_83XX_CLKIN in all
  MPC83xx config files

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/configs/MPC837XERDB_defconfig b/configs/MPC837XERDB_defconfig
index 45b68e9..090b9e5 100644
--- a/configs/MPC837XERDB_defconfig
+++ b/configs/MPC837XERDB_defconfig
@@ -1,9 +1,11 @@
 CONFIG_PPC=y
 CONFIG_SYS_TEXT_BASE=0xFE000000
+CONFIG_SYS_CLK_FREQ=66666667
 CONFIG_MPC83xx=y
 CONFIG_TARGET_MPC837XERDB=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
+CONFIG_SYS_EXTRA_OPTIONS="PCIE"
 CONFIG_BOOTDELAY=6
 CONFIG_MISC_INIT_R=y
 CONFIG_HUSH_PARSER=y