Generic udelay() with watchdog support

According to the PPC reference implementation the udelay() function is
responsible for resetting the watchdog timer as frequently as needed.
Most other architectures do not meet that requirement, so long-running
operations might result in a watchdog reset.

This patch adds a generic udelay() function which takes care of
resetting the watchdog before calling an architecture-specific
__udelay().

Signed-off-by: Ingo van Lil <inguin@gmx.de>
diff --git a/board/armltd/integrator/timer.c b/board/armltd/integrator/timer.c
index 087cf59..7562ffa 100644
--- a/board/armltd/integrator/timer.c
+++ b/board/armltd/integrator/timer.c
@@ -124,7 +124,7 @@
 }
 
 /* delay usec useconds */
-void udelay (unsigned long usec)
+void __udelay (unsigned long usec)
 {
 	ulong tmo, tmp;
 
diff --git a/board/freescale/mpc8313erdb/sdram.c b/board/freescale/mpc8313erdb/sdram.c
index cb13829..0c4fd68 100644
--- a/board/freescale/mpc8313erdb/sdram.c
+++ b/board/freescale/mpc8313erdb/sdram.c
@@ -72,7 +72,7 @@
 	 * Erratum DDR3 requires a 50ms delay after clearing DDRCDR[DDR_cfg],
 	 * or the DDR2 controller may fail to initialize correctly.
 	 */
-	udelay(50000);
+	__udelay(50000);
 
 	im->ddr.csbnds[0].csbnds = (msize - 1) >> 24;
 	im->ddr.cs_config[0] = CONFIG_SYS_DDR_CONFIG;