a320evb: fix udelay / __udelay confusion

Fix the following compiler problems:

arch/arm/cpu/arm920t/a320/liba320.a(timer.o): In function `udelay':
/home/wd/git/u-boot/work/arch/arm/cpu/arm920t/a320/timer.c:160: multiple definition of `udelay'
lib/libgeneric.a(time.o):/home/wd/git/u-boot/work/lib/time.c:34: first defined here
lib/libgeneric.a(time.o): In function `udelay':
time.c:(.text+0x1c): undefined reference to `__udelay'

Signed-off-by: Wolfgang Denk <wd@denx.de>

arch/arm/cpu/arm920t/a320/timer.c

@@ -156,7 +156,7 @@ void set_timer(ulong t)
 }
 
 /* delay x useconds AND preserve advance timestamp value */
-void udelay(unsigned long usec)
+void __udelay(unsigned long usec)
 {
 	long tmo = usec * (TIMER_CLOCK / 1000) / 1000;
 	unsigned long now, last = readl(&tmr->timer3_counter);