IMX: MX31: Cleanup include files and drop nasty #ifdef in drivers

As exception among the i.MX processors, the i.MX31 has headers
without general names (mx31-regs.h, mx31.h instead of imx-regs.h and
clock.h). This requires several nasty #ifdef in the drivers to
include the correct header. The patch cleans up the driver and
renames the header files as for the other i.MX processors.

Signed-off-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/cpu/arm1136/mx31/timer.c b/arch/arm/cpu/arm1136/mx31/timer.c
index 27c340f..c4bc3b3 100644
--- a/arch/arm/cpu/arm1136/mx31/timer.c
+++ b/arch/arm/cpu/arm1136/mx31/timer.c
@@ -22,7 +22,7 @@
  */
 
 #include <common.h>
-#include <asm/arch/mx31-regs.h>
+#include <asm/arch/imx-regs.h>
 #include <div64.h>
 #include <watchdog.h>
 #include <asm/io.h>