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/arm920t/imx/timer.c b/arch/arm/cpu/arm920t/imx/timer.c
index cd9b546..9289905 100644
--- a/arch/arm/cpu/arm920t/imx/timer.c
+++ b/arch/arm/cpu/arm920t/imx/timer.c
@@ -46,7 +46,7 @@
 	return TCN1;
 }
 
-void udelay_masked (unsigned long usec)
+void __udelay (unsigned long usec)
 {
 	ulong endtime = get_timer_masked() + usec;
 	signed long diff;
@@ -57,11 +57,6 @@
 	} while (diff >= 0);
 }
 
-void __udelay (unsigned long usec)
-{
-	udelay_masked(usec);
-}
-
 /*
  * This function is derived from PowerPC code (read timebase as long long).
  * On ARM it just returns the timer value.