ppc4xx: Consolidate some of the 405 and 440 macros/structs into 4xx

This patch moves some common 4xx macros and the PPC405_SYS_INFO/
PPC440_SYS_INFO structure into the common ppc4xx.h header.

Lot's of other macros are good candidates to be consolidated this way
in the future.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/cpu/ppc4xx/40x_spd_sdram.c b/cpu/ppc4xx/40x_spd_sdram.c
index 19c4f76..42fd7fb 100644
--- a/cpu/ppc4xx/40x_spd_sdram.c
+++ b/cpu/ppc4xx/40x_spd_sdram.c
@@ -148,7 +148,7 @@
 	int t_rc;
 	int min_cas;
 
-	PPC405_SYS_INFO sys_info;
+	PPC4xx_SYS_INFO sys_info;
 	unsigned long bus_period_x_10;
 
 	/*