arm: remove prototype for udelay_masked

The interruption support had be removed for ARM architecture and
the function udelay_masked() is no more used except in some timer.c
files  and have the same content than udelay() or __udelay().

This patch update each timer.c implementing this function and
remove the associated prototype in u-boot-arm.h.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/arch/arm/cpu/sa1100/timer.c b/arch/arm/cpu/sa1100/timer.c
index 12514e4..c7829c9 100644
--- a/arch/arm/cpu/sa1100/timer.c
+++ b/arch/arm/cpu/sa1100/timer.c
@@ -17,17 +17,12 @@
 	return get_timer_masked ();
 }
 
-void __udelay (unsigned long usec)
-{
-	udelay_masked (usec);
-}
-
 ulong get_timer_masked (void)
 {
 	return OSCR;
 }
 
-void udelay_masked (unsigned long usec)
+void __udelay (unsigned long usec)
 {
 	ulong tmo;
 	ulong endtime;