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/arch/powerpc/cpu/mpc83xx/speed.c b/arch/powerpc/cpu/mpc83xx/speed.c
index 668ed27..e870a23 100644
--- a/arch/powerpc/cpu/mpc83xx/speed.c
+++ b/arch/powerpc/cpu/mpc83xx/speed.c
@@ -137,8 +137,8 @@
 	clkin_div = ((im->clk.spmr & SPMR_CKID) >> SPMR_CKID_SHIFT);
 
 	if (im->reset.rcwh & HRCWH_PCI_HOST) {
-#if defined(CONFIG_83XX_CLKIN)
-		pci_sync_in = CONFIG_83XX_CLKIN / (1 + clkin_div);
+#if defined(CONFIG_SYS_CLK_FREQ)
+		pci_sync_in = CONFIG_SYS_CLK_FREQ / (1 + clkin_div);
 #else
 		pci_sync_in = 0xDEADBEEF;
 #endif