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/mach-at91/arm920t/timer.c b/arch/arm/mach-at91/arm920t/timer.c
index bbe90ae..6a98d7c 100644
--- a/arch/arm/mach-at91/arm920t/timer.c
+++ b/arch/arm/mach-at91/arm920t/timer.c
@@ -58,11 +58,6 @@
 	return get_timer_masked() - base;
 }
 
-void __udelay(unsigned long usec)
-{
-	udelay_masked(usec);
-}
-
 ulong get_timer_raw(void)
 {
 	at91_tc_t *tc = (at91_tc_t *) ATMEL_BASE_TC;
@@ -87,7 +82,7 @@
 	return get_timer_raw()/TIMER_LOAD_VAL;
 }
 
-void udelay_masked(unsigned long usec)
+void __udelay(unsigned long usec)
 {
 	u32 tmo;
 	u32 endtime;