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/board/tqc/tqm834x/pci.c b/board/tqc/tqm834x/pci.c
index 34c68ac..c9b05e4 100644
--- a/board/tqc/tqm834x/pci.c
+++ b/board/tqc/tqm834x/pci.c
@@ -71,7 +71,7 @@
 	reg32 = 0xff000000;
 #endif
 	if (clk->spmr & SPMR_CKID) {
-		/* PCI Clock is half CONFIG_83XX_CLKIN so need to set up OCCR
+		/* PCI Clock is half CONFIG_SYS_CLK_FREQ so need to set up OCCR
 		 * fields accordingly */
 		reg32 |= (OCCR_PCI1CR | OCCR_PCI2CR);